auth dev-fixed-code bypasses attempts cap; dev-deploy gains manual dispatch

Two problems showed up while trying to log into the long-lived dev
environment with the dev-fixed code `123456`:

1. `ConfirmEmailCode` checked the per-challenge attempts ceiling
   *before* the dev-fixed-code override. A developer who burned past
   `ChallengeMaxAttempts` on an existing un-consumed challenge (easy
   to trigger when the throttle reuses one challenge_id) hit
   `ErrTooManyAttempts` and the UI rendered "code expired or already
   used" even though the fixed code was correct. Reorder so the
   dev-fixed-code branch runs first and bypasses both the bcrypt
   verify and the attempts gate. Production stays unaffected
   because production loaders refuse to set `DevFixedCode`.

2. `dev-deploy.yaml` only fires on push to `development`, so the
   matching docker-compose default change for
   `BACKEND_AUTH_DEV_FIXED_CODE` could not reach the running stack
   before this PR merged. Add `workflow_dispatch: {}` so a developer
   can deploy any branch — typically a feature branch under review —
   from the Gitea Actions UI without waiting for the merge.

Covered by a new `TestConfirmEmailCodeDevFixedCodeBypassesAttemptsCeiling`
integration test that burns through the ceiling with wrong codes
then proves the dev-fixed code still produces a session.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/internal/auth/auth_e2e_test.go

@@ -513,6 +513,52 @@ func TestConfirmEmailCodeWrongCode(t *testing.T) {
 	}
 }
 
+// TestConfirmEmailCodeDevFixedCodeBypassesAttemptsCeiling proves the
+// dev-mode override is a true escape hatch: a developer who already
+// burned past ChallengeMaxAttempts on a long-lived dev challenge
+// (typically because the throttle merged repeated send-email-code
+// calls onto one challenge_id) can still recover by submitting the
+// fixed code without first waiting out the challenge TTL.
+func TestConfirmEmailCodeDevFixedCodeBypassesAttemptsCeiling(t *testing.T) {
+	db := startPostgres(t)
+	cfg := authConfig()
+	cfg.DevFixedCode = "999999"
+	svc := buildServiceWithConfig(t, db, cfg)
+	ctx := context.Background()
+
+	id, err := svc.SendEmailCode(ctx, "dev-bypass-ceiling@example.test", "en", "", "")
+	if err != nil {
+		t.Fatalf("send: %v", err)
+	}
+
+	// Burn through the attempts ceiling with deliberately wrong codes.
+	for i := range cfg.ChallengeMaxAttempts + 1 {
+		_, err := svc.ConfirmEmailCode(ctx, auth.ConfirmInputs{
+			ChallengeID:     id,
+			Code:            "111111",
+			ClientPublicKey: randomKey(t),
+			TimeZone:        "UTC",
+		})
+		if err == nil {
+			t.Fatalf("attempt %d unexpectedly succeeded", i)
+		}
+	}
+
+	// The dev-fixed code still goes through.
+	session, err := svc.ConfirmEmailCode(ctx, auth.ConfirmInputs{
+		ChallengeID:     id,
+		Code:            "999999",
+		ClientPublicKey: randomKey(t),
+		TimeZone:        "UTC",
+	})
+	if err != nil {
+		t.Fatalf("dev-fixed-code after attempts exhausted: %v", err)
+	}
+	if session.DeviceSessionID == uuid.Nil {
+		t.Fatalf("dev-fixed-code did not produce a session")
+	}
+}
+
 func TestConfirmEmailCodeAttemptsCeiling(t *testing.T) {
 	db := startPostgres(t)
 	svc, mailer, _, _ := buildService(t, db)

backend/internal/auth/challenge.go

@@ -163,15 +163,28 @@ func (s *Service) ConfirmEmailCode(ctx context.Context, in ConfirmInputs) (Sessi
 		return Session{}, err
 	}
 
-	if int(loaded.Attempts) > s.deps.Config.ChallengeMaxAttempts {
-		s.deps.Logger.Info("auth challenge attempts exhausted",
+	// The dev-mode fixed-code override is checked first so it bypasses
+	// both the bcrypt verify and the per-challenge attempts ceiling.
+	// Without this, a developer who already burned through
+	// `ChallengeMaxAttempts` on an existing un-consumed challenge —
+	// for example after the throttle merged repeated send-email-code
+	// calls onto one challenge_id — could not recover with the fixed
+	// code either, defeating the purpose of the override. Production
+	// deployments leave `DevFixedCode` empty, so this branch is
+	// inert and the regular attempts gate still applies.
+	if s.devFixedCodeMatches(in.Code) {
+		s.deps.Logger.Warn("auth challenge accepted via dev-mode fixed code override",
 			zap.String("challenge_id", in.ChallengeID.String()),
 			zap.Int32("attempts", loaded.Attempts),
 		)
-		return Session{}, ErrTooManyAttempts
-	}
-
-	if !s.devFixedCodeMatches(in.Code) {
+	} else {
+		if int(loaded.Attempts) > s.deps.Config.ChallengeMaxAttempts {
+			s.deps.Logger.Info("auth challenge attempts exhausted",
+				zap.String("challenge_id", in.ChallengeID.String()),
+				zap.Int32("attempts", loaded.Attempts),
+			)
+			return Session{}, ErrTooManyAttempts
+		}
 		if err := verifyCode(loaded.CodeHash, in.Code); err != nil {
 			if errors.Is(err, ErrCodeMismatch) {
 				s.deps.Logger.Info("auth challenge code mismatch",
@@ -182,10 +195,6 @@ func (s *Service) ConfirmEmailCode(ctx context.Context, in ConfirmInputs) (Sessi
 			}
 			return Session{}, err
 		}
-	} else {
-		s.deps.Logger.Warn("auth challenge accepted via dev-mode fixed code override",
-			zap.String("challenge_id", in.ChallengeID.String()),
-		)
 	}
 
 	// Re-check permanent_block after verifying the code. SendEmailCode