feat(banner): per-campaign colour overrides and urgent alerts

Non-default campaigns gain an optional colour override (background / text /
link) in two sets — one for every theme, one for the dark theme only — and an
"urgent" flag.

- Colours ride profile.get as six trailing FlatBuffers strings on
  BannerCampaign (backward-compatible). The client resolves the cascade
  (dark <- dark ?? all, light <- all) per rendered theme and derives the strip
  border from the background in JS (no CSS color-mix, for the old Android
  WebView floor); AdBanner applies them as inline vars scoped to the strip.
- Urgent is resolved entirely server-side: while any enabled, in-window urgent
  campaign exists, computeActiveSet returns only the urgent campaigns and
  bannerFor skips the eligibility gate — so a system notice reaches every viewer
  (paid / hint-holding / no_banner included) and preempts the ordinary feed. No
  wire field; it appears on each viewer's next profile.get.
- Admin console (/_gm/banners): native colour pickers + a live light/dark
  preview of the strip, and an urgent toggle. The default campaign stays plain,
  enforced by the service and a DB CHECK.

Migration 00009 is additive (nullable colour columns + a bool default +
all-or-nothing / hex / default-plain CHECKs) — expand-contract, rollback-safe.

Docs: ARCHITECTURE §10, UI_DESIGN, FUNCTIONAL (+ru). Tests: ads unit (urgent
preempt + colour validation), codec + resolver unit, gateway transcode, and
integration (colour round-trip + urgent bypass against real Postgres).

backend/internal/postgres/jet/backend/model/ad_campaigns.go

@@ -13,13 +13,20 @@ import (
 )
 
 type AdCampaigns struct {
-	CampaignID uuid.UUID `sql:"primary_key"`
-	Name       string
-	Weight     int32
-	IsDefault  bool
-	Enabled    bool
-	StartsAt   *time.Time
-	EndsAt     *time.Time
-	CreatedAt  time.Time
-	UpdatedAt  time.Time
+	CampaignID       uuid.UUID `sql:"primary_key"`
+	Name             string
+	Weight           int32
+	IsDefault        bool
+	Enabled          bool
+	StartsAt         *time.Time
+	EndsAt           *time.Time
+	CreatedAt        time.Time
+	UpdatedAt        time.Time
+	OverrideBg       *string
+	OverrideFg       *string
+	OverrideLink     *string
+	OverrideBgDark   *string
+	OverrideFgDark   *string
+	OverrideLinkDark *string
+	Urgent           bool
 }

backend/internal/postgres/jet/backend/table/ad_campaigns.go

@@ -17,15 +17,22 @@ type adCampaignsTable struct {
 	postgres.Table
 
 	// Columns
-	CampaignID postgres.ColumnString
-	Name       postgres.ColumnString
-	Weight     postgres.ColumnInteger
-	IsDefault  postgres.ColumnBool
-	Enabled    postgres.ColumnBool
-	StartsAt   postgres.ColumnTimestampz
-	EndsAt     postgres.ColumnTimestampz
-	CreatedAt  postgres.ColumnTimestampz
-	UpdatedAt  postgres.ColumnTimestampz
+	CampaignID       postgres.ColumnString
+	Name             postgres.ColumnString
+	Weight           postgres.ColumnInteger
+	IsDefault        postgres.ColumnBool
+	Enabled          postgres.ColumnBool
+	StartsAt         postgres.ColumnTimestampz
+	EndsAt           postgres.ColumnTimestampz
+	CreatedAt        postgres.ColumnTimestampz
+	UpdatedAt        postgres.ColumnTimestampz
+	OverrideBg       postgres.ColumnString
+	OverrideFg       postgres.ColumnString
+	OverrideLink     postgres.ColumnString
+	OverrideBgDark   postgres.ColumnString
+	OverrideFgDark   postgres.ColumnString
+	OverrideLinkDark postgres.ColumnString
+	Urgent           postgres.ColumnBool
 
 	AllColumns     postgres.ColumnList
 	MutableColumns postgres.ColumnList
@@ -67,33 +74,47 @@ func newAdCampaignsTable(schemaName, tableName, alias string) *AdCampaignsTable
 
 func newAdCampaignsTableImpl(schemaName, tableName, alias string) adCampaignsTable {
 	var (
-		CampaignIDColumn = postgres.StringColumn("campaign_id")
-		NameColumn       = postgres.StringColumn("name")
-		WeightColumn     = postgres.IntegerColumn("weight")
-		IsDefaultColumn  = postgres.BoolColumn("is_default")
-		EnabledColumn    = postgres.BoolColumn("enabled")
-		StartsAtColumn   = postgres.TimestampzColumn("starts_at")
-		EndsAtColumn     = postgres.TimestampzColumn("ends_at")
-		CreatedAtColumn  = postgres.TimestampzColumn("created_at")
-		UpdatedAtColumn  = postgres.TimestampzColumn("updated_at")
-		allColumns       = postgres.ColumnList{CampaignIDColumn, NameColumn, WeightColumn, IsDefaultColumn, EnabledColumn, StartsAtColumn, EndsAtColumn, CreatedAtColumn, UpdatedAtColumn}
-		mutableColumns   = postgres.ColumnList{NameColumn, WeightColumn, IsDefaultColumn, EnabledColumn, StartsAtColumn, EndsAtColumn, CreatedAtColumn, UpdatedAtColumn}
-		defaultColumns   = postgres.ColumnList{IsDefaultColumn, EnabledColumn, CreatedAtColumn, UpdatedAtColumn}
+		CampaignIDColumn       = postgres.StringColumn("campaign_id")
+		NameColumn             = postgres.StringColumn("name")
+		WeightColumn           = postgres.IntegerColumn("weight")
+		IsDefaultColumn        = postgres.BoolColumn("is_default")
+		EnabledColumn          = postgres.BoolColumn("enabled")
+		StartsAtColumn         = postgres.TimestampzColumn("starts_at")
+		EndsAtColumn           = postgres.TimestampzColumn("ends_at")
+		CreatedAtColumn        = postgres.TimestampzColumn("created_at")
+		UpdatedAtColumn        = postgres.TimestampzColumn("updated_at")
+		OverrideBgColumn       = postgres.StringColumn("override_bg")
+		OverrideFgColumn       = postgres.StringColumn("override_fg")
+		OverrideLinkColumn     = postgres.StringColumn("override_link")
+		OverrideBgDarkColumn   = postgres.StringColumn("override_bg_dark")
+		OverrideFgDarkColumn   = postgres.StringColumn("override_fg_dark")
+		OverrideLinkDarkColumn = postgres.StringColumn("override_link_dark")
+		UrgentColumn           = postgres.BoolColumn("urgent")
+		allColumns             = postgres.ColumnList{CampaignIDColumn, NameColumn, WeightColumn, IsDefaultColumn, EnabledColumn, StartsAtColumn, EndsAtColumn, CreatedAtColumn, UpdatedAtColumn, OverrideBgColumn, OverrideFgColumn, OverrideLinkColumn, OverrideBgDarkColumn, OverrideFgDarkColumn, OverrideLinkDarkColumn, UrgentColumn}
+		mutableColumns         = postgres.ColumnList{NameColumn, WeightColumn, IsDefaultColumn, EnabledColumn, StartsAtColumn, EndsAtColumn, CreatedAtColumn, UpdatedAtColumn, OverrideBgColumn, OverrideFgColumn, OverrideLinkColumn, OverrideBgDarkColumn, OverrideFgDarkColumn, OverrideLinkDarkColumn, UrgentColumn}
+		defaultColumns         = postgres.ColumnList{IsDefaultColumn, EnabledColumn, CreatedAtColumn, UpdatedAtColumn, UrgentColumn}
 	)
 
 	return adCampaignsTable{
 		Table: postgres.NewTable(schemaName, tableName, alias, allColumns...),
 
 		//Columns
-		CampaignID: CampaignIDColumn,
-		Name:       NameColumn,
-		Weight:     WeightColumn,
-		IsDefault:  IsDefaultColumn,
-		Enabled:    EnabledColumn,
-		StartsAt:   StartsAtColumn,
-		EndsAt:     EndsAtColumn,
-		CreatedAt:  CreatedAtColumn,
-		UpdatedAt:  UpdatedAtColumn,
+		CampaignID:       CampaignIDColumn,
+		Name:             NameColumn,
+		Weight:           WeightColumn,
+		IsDefault:        IsDefaultColumn,
+		Enabled:          EnabledColumn,
+		StartsAt:         StartsAtColumn,
+		EndsAt:           EndsAtColumn,
+		CreatedAt:        CreatedAtColumn,
+		UpdatedAt:        UpdatedAtColumn,
+		OverrideBg:       OverrideBgColumn,
+		OverrideFg:       OverrideFgColumn,
+		OverrideLink:     OverrideLinkColumn,
+		OverrideBgDark:   OverrideBgDarkColumn,
+		OverrideFgDark:   OverrideFgDarkColumn,
+		OverrideLinkDark: OverrideLinkDarkColumn,
+		Urgent:           UrgentColumn,
 
 		AllColumns:     allColumns,
 		MutableColumns: mutableColumns,

backend/internal/postgres/migrations/00009_banner_colors_urgent.sql

@@ -0,0 +1,60 @@
+-- Per-campaign banner colour overrides and the urgent (always-show) flag.
+--
+-- ad_campaigns gains two optional colour sets and an urgent flag, all for
+-- non-default campaigns only:
+--   override_bg/fg/link           — paints the strip on every theme
+--   override_bg/fg/link_dark      — further overrides the dark theme
+--   urgent                        — force the banner on every viewer (bypassing
+--                                   eligibility) and suppress all non-urgent
+--                                   campaigns while any urgent one is active
+--
+-- Each colour set is all-or-nothing (bg+fg+link together, or absent) and every
+-- colour is a "#rrggbb" hex string. The default (house) campaign stays plain: no
+-- colours, never urgent.
+--
+-- Expand-contract: additive (nullable columns plus one NOT NULL boolean with a
+-- default), so a backend image rollback stays DB-safe — older code ignores them.
+-- The ad_campaigns table shape changes, so its generated go-jet model is
+-- regenerated (by hand here, to keep the diff to this one table).
+
+-- +goose Up
+ALTER TABLE backend.ad_campaigns
+    ADD COLUMN override_bg text,
+    ADD COLUMN override_fg text,
+    ADD COLUMN override_link text,
+    ADD COLUMN override_bg_dark text,
+    ADD COLUMN override_fg_dark text,
+    ADD COLUMN override_link_dark text,
+    ADD COLUMN urgent boolean DEFAULT false NOT NULL,
+    ADD CONSTRAINT ad_campaigns_override_all_chk CHECK (
+        (override_bg IS NULL AND override_fg IS NULL AND override_link IS NULL)
+        OR (override_bg IS NOT NULL AND override_fg IS NOT NULL AND override_link IS NOT NULL)
+    ),
+    ADD CONSTRAINT ad_campaigns_override_dark_chk CHECK (
+        (override_bg_dark IS NULL AND override_fg_dark IS NULL AND override_link_dark IS NULL)
+        OR (override_bg_dark IS NOT NULL AND override_fg_dark IS NOT NULL AND override_link_dark IS NOT NULL)
+    ),
+    ADD CONSTRAINT ad_campaigns_override_hex_chk CHECK (
+        (override_bg IS NULL OR override_bg ~ '^#[0-9a-fA-F]{6}$')
+        AND (override_fg IS NULL OR override_fg ~ '^#[0-9a-fA-F]{6}$')
+        AND (override_link IS NULL OR override_link ~ '^#[0-9a-fA-F]{6}$')
+        AND (override_bg_dark IS NULL OR override_bg_dark ~ '^#[0-9a-fA-F]{6}$')
+        AND (override_fg_dark IS NULL OR override_fg_dark ~ '^#[0-9a-fA-F]{6}$')
+        AND (override_link_dark IS NULL OR override_link_dark ~ '^#[0-9a-fA-F]{6}$')
+    ),
+    ADD CONSTRAINT ad_campaigns_default_plain_chk CHECK (
+        (NOT is_default)
+        OR (override_bg IS NULL AND override_fg IS NULL AND override_link IS NULL
+            AND override_bg_dark IS NULL AND override_fg_dark IS NULL AND override_link_dark IS NULL
+            AND NOT urgent)
+    );
+
+-- +goose Down
+ALTER TABLE backend.ad_campaigns
+    DROP COLUMN override_bg,
+    DROP COLUMN override_fg,
+    DROP COLUMN override_link,
+    DROP COLUMN override_bg_dark,
+    DROP COLUMN override_fg_dark,
+    DROP COLUMN override_link_dark,
+    DROP COLUMN urgent;