R3: backend rate-limit observability — ratewatch, auto-flag, admin throttled view

- accounts.flagged_high_rate_at baked into the R1 baseline (no prod data; the
  contour schema is wiped after merge); jet regenerated — the regen also picks
  up the previously missing game_drafts/game_hidden models.
- account.Store: FlagHighRate (set-once), ClearHighRateFlag, the flag in
  GetByID/ListUsers and a ListFlaggedHighRate review queue.
- New internal/ratewatch: ingests the gateway rejection reports, keeps a
  bounded in-memory episode window for the console and applies the
  conservative auto-flag (1000 rejected / 10 min, BACKEND_HIGHRATE_FLAG_*).
- POST /api/v1/internal/ratelimit/report (network-trusted, like
  sessions/resolve).
- Admin console: Throttled page (episodes + flagged accounts), a high-rate
  badge in the user list, the marker + operator clear action on the user card.
- Tests: ratewatch unit suite, report-route handler test, renderer cases,
  integration coverage for the store round-trip and the console flow.

backend/internal/account/userlist.go

@@ -2,6 +2,7 @@ package account
 
 import (
 	"context"
+	"database/sql"
 	"fmt"
 	"strings"
 	"time"
@@ -18,6 +19,9 @@ type UserListItem struct {
 	PreferredLanguage string
 	IsGuest           bool
 	IsRobot           bool
+	// FlaggedHighRateAt is the soft high-rate marker (zero when unflagged), shown
+	// as a badge in the console list (R3).
+	FlaggedHighRateAt time.Time
 	CreatedAt         time.Time
 }
 
@@ -65,7 +69,7 @@ func userListWhere(f UserFilter) (string, []any) {
 // ListUsers returns the filtered admin user list, newest first, paginated.
 func (s *Store) ListUsers(ctx context.Context, f UserFilter, limit, offset int) ([]UserListItem, error) {
 	where, args := userListWhere(f)
-	q := `SELECT a.account_id, a.display_name, a.preferred_language, a.is_guest, a.created_at, ` + robotExists + ` AS is_robot
+	q := `SELECT a.account_id, a.display_name, a.preferred_language, a.is_guest, a.flagged_high_rate_at, a.created_at, ` + robotExists + ` AS is_robot
 FROM backend.accounts a WHERE ` + where +
 		fmt.Sprintf(` ORDER BY a.created_at DESC LIMIT $%d OFFSET $%d`, len(args)+1, len(args)+2)
 	args = append(args, limit, offset)
@@ -77,14 +81,51 @@ FROM backend.accounts a WHERE ` + where +
 	var out []UserListItem
 	for rows.Next() {
 		var it UserListItem
-		if err := rows.Scan(&it.ID, &it.DisplayName, &it.PreferredLanguage, &it.IsGuest, &it.CreatedAt, &it.IsRobot); err != nil {
+		var flagged sql.NullTime
+		if err := rows.Scan(&it.ID, &it.DisplayName, &it.PreferredLanguage, &it.IsGuest, &flagged, &it.CreatedAt, &it.IsRobot); err != nil {
 			return nil, fmt.Errorf("account: scan user: %w", err)
 		}
+		if flagged.Valid {
+			it.FlaggedHighRateAt = flagged.Time
+		}
 		out = append(out, it)
 	}
 	return out, rows.Err()
 }
 
+// FlaggedAccount is one row of the console's high-rate review queue.
+type FlaggedAccount struct {
+	ID                uuid.UUID
+	DisplayName       string
+	FlaggedHighRateAt time.Time
+}
+
+// flaggedListCap bounds the console's flagged-account list; the operator clears
+// flags as they are reviewed, so the queue stays short in practice.
+const flaggedListCap = 200
+
+// ListFlaggedHighRate returns the accounts carrying the high-rate flag, most
+// recently flagged first (R3).
+func (s *Store) ListFlaggedHighRate(ctx context.Context) ([]FlaggedAccount, error) {
+	rows, err := s.db.QueryContext(ctx,
+		`SELECT account_id, display_name, flagged_high_rate_at
+FROM backend.accounts WHERE flagged_high_rate_at IS NOT NULL
+ORDER BY flagged_high_rate_at DESC LIMIT $1`, flaggedListCap)
+	if err != nil {
+		return nil, fmt.Errorf("account: list flagged: %w", err)
+	}
+	defer rows.Close()
+	var out []FlaggedAccount
+	for rows.Next() {
+		var fa FlaggedAccount
+		if err := rows.Scan(&fa.ID, &fa.DisplayName, &fa.FlaggedHighRateAt); err != nil {
+			return nil, fmt.Errorf("account: scan flagged: %w", err)
+		}
+		out = append(out, fa)
+	}
+	return out, rows.Err()
+}
+
 // CountUsers counts the filtered admin user list, for pagination.
 func (s *Store) CountUsers(ctx context.Context, f UserFilter) (int, error) {
 	where, args := userListWhere(f)