feat(telegram): bot support relay — per-user forum topics

Users who DM the bot anything but /start are relayed into a private
forum supergroup, one topic per user. Operators (the chat's admins)
reply in the topic and the bot copies it back to the user; an info card
opening each topic carries a Block/Unblock toggle and a Clear button.
State is a small JSON file on a new /data volume — the bot host has no
database. Off by default (TELEGRAM_SUPPORT_CHAT_ID=0): the prod bot is
unchanged until the operator sets the chat id and adds the bot as a
forum admin.

- internal/support: concurrency-safe JSON store (topic map, block list,
  relayed message ids) with field-targeted mutators and atomic save
- bot/support.go: relay both ways via copyMessage, short-TTL admin
  cache, callback buttons, per-user topic-create lock, loop guard
  (skip the bot's own posts), reopen a deleted topic on the next message
- config + compose + CI/prod-deploy: TELEGRAM_SUPPORT_CHAT_ID per
  contour + TELEGRAM_SUPPORT_STATE_DIR; bot-state named volume; /data
  pre-owned by UID 65532 so a fresh volume is writable under distroless
- docs: ARCHITECTURE §15 + decision record, FUNCTIONAL (+ru), README

platform/telegram/cmd/bot/main.go

@@ -10,6 +10,7 @@ import (
 	"context"
 	"log"
 	"os/signal"
+	"path/filepath"
 	"sync"
 	"syscall"
 	"time"
@@ -23,6 +24,7 @@ import (
 	"scrabble/platform/telegram/internal/botlink"
 	"scrabble/platform/telegram/internal/config"
 	"scrabble/platform/telegram/internal/promobot"
+	"scrabble/platform/telegram/internal/support"
 )
 
 // telemetryShutdownTimeout bounds the OpenTelemetry flush during process exit.
@@ -65,6 +67,19 @@ func run(ctx context.Context, cfg config.BotConfig, logger *zap.Logger) error {
 		logger.Warn("telemetry: start runtime metrics", zap.Error(err))
 	}
 
+	// The support relay keeps its per-user state in a JSON file on a writable volume
+	// (the bot host has no database). A corrupt file is logged and the relay starts
+	// empty rather than crash-looping the bot.
+	var supportStore *support.Store
+	if cfg.SupportChatID != 0 {
+		statePath := filepath.Join(cfg.SupportStateDir, "support.json")
+		supportStore, err = support.Open(statePath)
+		if err != nil {
+			logger.Warn("support: state load failed, starting empty", zap.String("path", statePath), zap.Error(err))
+			supportStore = support.New(statePath)
+		}
+	}
+
 	b, err := bot.New(bot.Config{
 		Token:             cfg.Token,
 		APIBaseURL:        cfg.APIBaseURL,
@@ -73,6 +88,8 @@ func run(ctx context.Context, cfg config.BotConfig, logger *zap.Logger) error {
 		SendRatePerSecond: cfg.SendRatePerSecond,
 		ChatID:            cfg.ChatID,
 		GameChannelID:     cfg.GameChannelID,
+		SupportChatID:     cfg.SupportChatID,
+		SupportStore:      supportStore,
 	}, logger)
 	if err != nil {
 		return err
@@ -128,6 +145,7 @@ func run(ctx context.Context, cfg config.BotConfig, logger *zap.Logger) error {
 		zap.Bool("owns_updates", cfg.OwnsUpdates),
 		zap.Bool("test_env", cfg.TestEnv),
 		zap.Bool("chat_gating", cfg.ChatID != 0),
+		zap.Bool("support_relay", cfg.SupportChatID != 0),
 		zap.Bool("promo_bot", promo != nil))
 
 	var wg sync.WaitGroup