feat(metadata): SQLite backend, storage reconciliation and local defaults

- pluggable per-domain Repository interfaces; PostgreSQL and SQLite impls
- SQLite on modernc.org/sqlite (WAL, busy_timeout, foreign_keys, immediate tx)
- separate migrations/sqlite and db.MigrateSQLite; store.NewPostgres/NewSQLite
- cmd/reconcile compares object storage with the journal (report, then --delete)
- storage.Backend.List and photos.Repository.AllStorageKeys
- DB_BACKEND/SQLITE_PATH and STORAGE_BACKEND/FS_ROOT selectable; local defaults
  (sqlite ./galo.db, fs ./data)
- Makefile reconcile/reconcile-delete; docs and .env.example updated

backend/internal/app/app.go

@@ -9,7 +9,6 @@ import (
 	"time"
 
 	"github.com/gin-gonic/gin"
-	"github.com/jackc/pgx/v5/pgxpool"
 
 	assets "shared-album"
 	"shared-album/internal/albums"
@@ -23,16 +22,17 @@ import (
 	"shared-album/internal/social"
 	"shared-album/internal/sse"
 	"shared-album/internal/storage"
+	"shared-album/internal/store"
 )
 
 type Server struct {
 	cfg     *config.Config
-	pool    *pgxpool.Pool
+	repos   store.Repos
+	ping    func(ctx context.Context) error
 	storage storage.Backend
 	hub     *sse.Hub
 
-	albumsStore *albums.Store
-	albums      *albums.Service
+	albums *albums.Service
 
 	auth *auth.Service
 
@@ -48,36 +48,30 @@ type Server struct {
 	share *sharelinks.Service
 }
 
-func New(cfg *config.Config, pool *pgxpool.Pool, st storage.Backend, hub *sse.Hub) *Server {
-	authStore := auth.NewStore(pool)
+// New wires the domain services over the selected metadata repositories. ping
+// reports the health of the metadata backend so health stays backend-agnostic.
+func New(cfg *config.Config, repos store.Repos, ping func(ctx context.Context) error, st storage.Backend, hub *sse.Hub) *Server {
 	tm := auth.NewTokenManager(cfg.Auth.JWTSecret, cfg.Auth.AccessTTL, cfg.Auth.RefreshTTL)
-	authSvc := auth.NewService(authStore, tm)
+	authSvc := auth.NewService(repos.Auth, tm)
 
-	albumsStore := albums.NewStore(pool)
-	membersStore := members.NewStore(pool)
+	notifSvc := notifications.NewService(repos.Notifications, hub)
 
-	notifStore := notifications.NewStore(pool)
-	notifSvc := notifications.NewService(notifStore, hub)
+	albumsSvc := albums.NewService(repos.Albums, repos.Members, hub, st)
+	membersSvc := members.NewService(repos.Members, repos.Albums, hub, notifSvc)
 
-	albumsSvc := albums.NewService(albumsStore, membersStore, hub, st)
-	membersSvc := members.NewService(membersStore, albumsStore, hub, notifSvc)
-
-	photosStore := photos.NewStore(pool)
-	photosSvc := photos.NewService(photosStore, albumsSvc, st, hub)
+	photosSvc := photos.NewService(repos.Photos, albumsSvc, st, hub)
 	photosWorker := photos.NewWorker(photosSvc, cfg.Worker.Interval, cfg.Worker.Batch, cfg.Worker.PendingTTL)
 
-	socialStore := social.NewStore(pool)
-	socialSvc := social.NewService(socialStore, albumsSvc, photosStore, hub, notifSvc)
+	socialSvc := social.NewService(repos.Social, albumsSvc, repos.Photos, hub, notifSvc)
 
-	shareStore := sharelinks.NewStore(pool)
-	shareSvc := sharelinks.NewService(shareStore, albumsSvc)
+	shareSvc := sharelinks.NewService(repos.ShareLinks, albumsSvc)
 
 	return &Server{
 		cfg:           cfg,
-		pool:          pool,
+		repos:         repos,
+		ping:          ping,
 		storage:       st,
 		hub:           hub,
-		albumsStore:   albumsStore,
 		albums:        albumsSvc,
 		auth:          authSvc,
 		membersSvc:    membersSvc,
@@ -183,7 +177,7 @@ func (s *Server) Router() *gin.Engine {
 func (s *Server) health(c *gin.Context) {
 	ctx := c.Request.Context()
 	dbStatus := "ok"
-	if err := s.pool.Ping(ctx); err != nil {
+	if err := s.ping(ctx); err != nil {
 		dbStatus = "error"
 	}
 	storageLabel := s.cfg.Storage.Backend
@@ -243,7 +237,7 @@ func (s *Server) shareAlbum(c *gin.Context) {
 		httpx.RespondError(c, err)
 		return
 	}
-	album, err := s.albumsStore.GetByID(c.Request.Context(), link.AlbumID)
+	album, err := s.repos.Albums.GetByID(c.Request.Context(), link.AlbumID)
 	if err != nil {
 		httpx.RespondError(c, httpx.NotFound("album_not_found", "album not found"))
 		return