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/inttest/admin_test.go

@@ -16,6 +16,7 @@ import (
 	"scrabble/backend/internal/account"
 	"scrabble/backend/internal/engine"
 	"scrabble/backend/internal/game"
+	"scrabble/backend/internal/ratewatch"
 	"scrabble/backend/internal/server"
 )
 
@@ -206,6 +207,72 @@ func TestConsoleGameDetailRobotSchedule(t *testing.T) {
 	}
 }
 
+// TestConsoleThrottledViewAndFlagClear drives the R3 rate-limit surface end to
+// end against real stores: a gateway report past the threshold auto-flags the
+// account, the throttled view shows the episode and the flagged account, the
+// user card carries the marker, and the operator clear (a same-origin POST)
+// reverses it.
+func TestConsoleThrottledViewAndFlagClear(t *testing.T) {
+	ctx := context.Background()
+	accounts := account.NewStore(testDB)
+	acc, err := accounts.ProvisionTelegram(ctx, "tg-"+uuid.NewString(), "en", "", "Throttled Player")
+	if err != nil {
+		t.Fatalf("provision: %v", err)
+	}
+
+	watch := ratewatch.New(ratewatch.Config{FlagThreshold: 100, FlagWindow: 10 * time.Minute}, accounts, zap.NewNop())
+	srv := server.New(":0", server.Deps{
+		Logger:    zap.NewNop(),
+		Accounts:  accounts,
+		Games:     newGameService(),
+		Registry:  testRegistry,
+		DictDir:   dictDir(),
+		RateWatch: watch,
+	})
+	h := srv.Handler()
+
+	report := `{"window_seconds":30,"entries":[` +
+		`{"class":"user","key":"` + acc.ID.String() + `","rejected":150},` +
+		`{"class":"public","key":"10.1.2.3","rejected":7}]}`
+	req := httptest.NewRequest(http.MethodPost, "http://admin.test/api/v1/internal/ratelimit/report", strings.NewReader(report))
+	req.Header.Set("Content-Type", "application/json")
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, req)
+	if rec.Code != http.StatusNoContent {
+		t.Fatalf("report = %d, want 204", rec.Code)
+	}
+
+	got, err := accounts.GetByID(ctx, acc.ID)
+	if err != nil {
+		t.Fatalf("get by id: %v", err)
+	}
+	if got.FlaggedHighRateAt.IsZero() {
+		t.Fatal("account not auto-flagged past the threshold")
+	}
+
+	base := "http://admin.test/_gm"
+	code, body := consoleDo(h, http.MethodGet, base+"/throttled", "", "")
+	if code != http.StatusOK || !strings.Contains(body, acc.ID.String()) ||
+		!strings.Contains(body, "10.1.2.3") || !strings.Contains(body, "Throttled Player") {
+		t.Fatalf("throttled view = %d, episode/flag shown = %v/%v",
+			code, strings.Contains(body, "10.1.2.3"), strings.Contains(body, "Throttled Player"))
+	}
+	if code, body = consoleDo(h, http.MethodGet, base+"/users/"+acc.ID.String(), "", ""); code != http.StatusOK || !strings.Contains(body, "Clear high-rate flag") {
+		t.Fatalf("user card = %d, has clear action = %v", code, strings.Contains(body, "Clear high-rate flag"))
+	}
+
+	// The clear POST is CSRF-guarded like every console action.
+	if code, _ = consoleDo(h, http.MethodPost, base+"/users/"+acc.ID.String()+"/clear-high-rate-flag", "", ""); code != http.StatusForbidden {
+		t.Fatalf("clear without origin = %d, want 403", code)
+	}
+	if code, body = consoleDo(h, http.MethodPost, base+"/users/"+acc.ID.String()+"/clear-high-rate-flag", "x=1", "http://admin.test"); code != http.StatusOK || !strings.Contains(body, "Cleared") {
+		t.Fatalf("clear with origin = %d, has Cleared = %v", code, strings.Contains(body, "Cleared"))
+	}
+	if got, err = accounts.GetByID(ctx, acc.ID); err != nil || !got.FlaggedHighRateAt.IsZero() {
+		t.Fatalf("flag survived the clear: %v (err %v)", got.FlaggedHighRateAt, err)
+	}
+}
+
 // consoleDo issues a request to h, optionally with an Origin header, and returns
 // the status and body. Form bodies are sent as application/x-www-form-urlencoded.
 func consoleDo(h http.Handler, method, target, body, origin string) (int, string) {