Auto-seed lookups + admin + templates on first API boot

Add a data_migration that runs seeds/001_lookups.sql,
seeds/003_admin_user.sql, and seeds/003_task_templates.sql exactly
once on startup and invalidates the Redis seeded_data cache afterwards
so /api/static_data/ returns fresh results. Removes the need to
remember `./dev.sh seed-all`; the data_migrations tracking row prevents
re-runs, and each INSERT uses ON CONFLICT DO UPDATE so re-execution is
safe.

cmd/api/main.go

@@ -81,6 +81,13 @@ func main() {
 		cache = nil
 	} else {
 		defer cache.Close()
+		if database.SeedInitialDataApplied {
+			if err := cache.InvalidateSeededData(context.Background()); err != nil {
+				log.Warn().Err(err).Msg("Failed to invalidate seeded data cache after initial seed")
+			} else {
+				log.Info().Msg("Invalidated seeded_data cache after initial seed migration")
+			}
+		}
 	}
 
 	// Initialize monitoring service (if Redis is available)