refactor: remove automatic background incremental sync

Garmin's rate-limiting means every unattended sync attempt risks a
ban; syncing should only ever happen when explicitly triggered via
"Sync now" (POST /api/sync/run), never on an unattended timer.

Removes the periodic background loop (main.go's runIncrementalSyncLoop,
api.Server.RunIncrementalSyncForAllUsers), its GENIUSRUN_INCREMENTAL_SYNC_EVERY
config, and store.DB.ListUsers (which existed solely to feed it). The
manual "Sync now" flow (Backfill/IncrementalSync/FillPendingDetails via
FullSync) is untouched.

backend/cmd/geniusrund/main.go

@@ -62,8 +62,6 @@ func main() {
 	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
 	defer stop()
 
-	go runIncrementalSyncLoop(ctx, server, cfg.IncrementalSyncEvery)
-
 	httpServer := &http.Server{Addr: cfg.Addr, Handler: server.Router()}
 	go func() {
 		log.Printf("geniusrund listening on %s", cfg.Addr)
@@ -80,19 +78,3 @@ func main() {
 		log.Printf("http server shutdown: %v", err)
 	}
 }
-
-// runIncrementalSyncLoop periodically syncs new activities for every
-// provisioned user in the background so the frontend doesn't need to
-// trigger every sync manually.
-func runIncrementalSyncLoop(ctx context.Context, server *api.Server, every time.Duration) {
-	ticker := time.NewTicker(every)
-	defer ticker.Stop()
-	for {
-		select {
-		case <-ctx.Done():
-			return
-		case <-ticker.C:
-			server.RunIncrementalSyncForAllUsers(ctx)
-		}
-	}
-}

backend/internal/api/server.go

@@ -264,31 +264,6 @@ func (s *Server) removeGarminClient(userID int64) {
 	}
 }
 
-// RunIncrementalSyncForAllUsers is called on a timer (see main.go) to sync
-// every provisioned user in turn, replacing the old single-global-Service
-// background loop.
-func (s *Server) RunIncrementalSyncForAllUsers(ctx context.Context) {
-	users, err := s.DB.ListUsers(ctx)
-	if err != nil {
-		log.Printf("api: list users for incremental sync: %v", err)
-		return
-	}
-	for _, u := range users {
-		svc, err := s.syncFor(ctx, u.ID)
-		if err != nil {
-			log.Printf("api: sync service for user %d: %v", u.ID, err)
-			continue
-		}
-		if err := svc.IncrementalSync(ctx); err != nil {
-			log.Printf("api: incremental sync for user %d: %v", u.ID, err)
-			continue
-		}
-		if err := svc.FillPendingDetails(ctx, 50); err != nil {
-			log.Printf("api: fill pending details for user %d: %v", u.ID, err)
-		}
-	}
-}
-
 var requestIDCounter atomic.Int64
 
 // requestLoggingMiddleware logs one JSON line per HTTP request (method,

backend/internal/config/config.go

@@ -36,7 +36,6 @@ type Config struct {
 	GarminTokenStoreRoot string
 
 	MinConfidence float64
-	IncrementalSyncEvery time.Duration
 	// LogLevel controls internal/applog's JSON logger ("debug"|"info"|"warn"|"error").
 	LogLevel string
 
@@ -76,7 +75,6 @@ func Load() (Config, error) {
 		GarminPythonPath:     getEnvDefault("GARMIN_WRAPPER_PYTHON", "python3"),
 		GarminTokenStoreRoot: os.Getenv("GARMIN_TOKENSTORE"),
 		MinConfidence:        getEnvFloat("GENIUSRUN_MIN_CONFIDENCE", 0.6),
-		IncrementalSyncEvery: getEnvDuration("GENIUSRUN_INCREMENTAL_SYNC_EVERY", 6*time.Hour),
 		LogLevel:             getEnvDefault("GENIUSRUN_LOG_LEVEL", "info"),
 		BackendURL:           strings.TrimRight(os.Getenv("GENIUSRUN_BACKEND_URL"), "/"),
 		OIDCIssuerURL:        os.Getenv("GENIUSRUN_OIDC_ISSUER_URL"),

backend/internal/store/users.go

@@ -32,26 +32,6 @@ func (db *DB) GetUserBySub(ctx context.Context, oidcSub string) (User, bool, err
 	return u, true, nil
 }
 
-// ListUsers returns every provisioned user, for the background incremental
-// sync loop to iterate.
-func (db *DB) ListUsers(ctx context.Context) ([]User, error) {
-	rows, err := db.QueryContext(ctx, `SELECT id, oidc_sub, display_name, created_at FROM users ORDER BY id`)
-	if err != nil {
-		return nil, fmt.Errorf("list users: %w", err)
-	}
-	defer rows.Close()
-
-	users := []User{}
-	for rows.Next() {
-		var u User
-		if err := rows.Scan(&u.ID, &u.OIDCSub, &u.DisplayName, &u.CreatedAt); err != nil {
-			return nil, fmt.Errorf("scan user row: %w", err)
-		}
-		users = append(users, u)
-	}
-	return users, rows.Err()
-}
-
 // neverMatchRule is the placeholder every fresh install's rule-engine kinds
 // start with -- every activity lands in needs_review until the user tunes
 // real rules.