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/e2e/sqlite_test.go

@@ -0,0 +1,150 @@
+package e2e
+
+import (
+	"bytes"
+	"context"
+	"database/sql"
+	"image"
+	"image/color"
+	"image/png"
+	"io/fs"
+	"path/filepath"
+	"testing"
+	"time"
+
+	assets "shared-album"
+	"shared-album/internal/albums"
+	"shared-album/internal/auth"
+	"shared-album/internal/db"
+	"shared-album/internal/photos"
+	"shared-album/internal/sse"
+	"shared-album/internal/storage"
+	"shared-album/internal/store"
+)
+
+func makePNG(t *testing.T) []byte {
+	t.Helper()
+	img := image.NewRGBA(image.Rect(0, 0, 4, 4))
+	for x := 0; x < 4; x++ {
+		for y := 0; y < 4; y++ {
+			img.Set(x, y, color.RGBA{R: uint8(x * 40), G: uint8(y * 40), B: 128, A: 255})
+		}
+	}
+	var buf bytes.Buffer
+	if err := png.Encode(&buf, img); err != nil {
+		t.Fatalf("encode png: %v", err)
+	}
+	return buf.Bytes()
+}
+
+type stack struct {
+	db     *sql.DB
+	photos *photos.Service
+	albums *albums.Service
+	auth   *auth.Service
+}
+
+// openStack opens a migrated SQLite database at path and builds the services.
+func openStack(t *testing.T, path, blobRoot string) (*stack, func()) {
+	t.Helper()
+	migFS, err := fs.Sub(assets.Migrations, "migrations/sqlite")
+	if err != nil {
+		t.Fatalf("migrations fs: %v", err)
+	}
+	if err := db.MigrateSQLite(path, migFS); err != nil {
+		t.Fatalf("migrate: %v", err)
+	}
+	database, err := db.OpenSQLite(path)
+	if err != nil {
+		t.Fatalf("open: %v", err)
+	}
+	repos := store.NewSQLite(database)
+	hub := sse.NewHub(1)
+	signer, err := storage.NewSigner("http://app.test", "secret", time.Hour)
+	if err != nil {
+		t.Fatalf("signer: %v", err)
+	}
+	blob, err := storage.NewFS(blobRoot, signer)
+	if err != nil {
+		t.Fatalf("fs: %v", err)
+	}
+	authSvc := auth.NewService(repos.Auth, auth.NewTokenManager("secret", 15*time.Minute, time.Hour))
+	albumsSvc := albums.NewService(repos.Albums, repos.Members, hub, blob)
+	photosSvc := photos.NewService(repos.Photos, albumsSvc, blob, hub)
+	return &stack{db: database, photos: photosSvc, albums: albumsSvc, auth: authSvc}, func() { database.Close() }
+}
+
+func TestSQLiteEndToEndWithRestart(t *testing.T) {
+	ctx := context.Background()
+	path := filepath.Join(t.TempDir(), "galo.db")
+	blobs := t.TempDir()
+
+	st, closeDB := openStack(t, path, blobs)
+	worker := photos.NewWorker(st.photos, 20*time.Millisecond, 10, time.Minute)
+	wctx, cancel := context.WithCancel(ctx)
+	go worker.Run(wctx)
+
+	user, _, err := st.auth.Register(ctx, "e2e@test.local", "password123", "E2E")
+	if err != nil {
+		t.Fatalf("register: %v", err)
+	}
+	album, err := st.albums.Create(ctx, user.ID, albums.CreateInput{Title: "Trip"})
+	if err != nil {
+		t.Fatalf("create album: %v", err)
+	}
+	p, err := st.photos.Upload(ctx, photos.UploadInput{AlbumID: album.ID, UserID: user.ID, Filename: "a.png", Data: makePNG(t)})
+	if err != nil {
+		t.Fatalf("upload: %v", err)
+	}
+	waitFor(t, "variants of first photo", func() bool {
+		got, err := st.photos.Get(ctx, p.ID, user.ID)
+		return err == nil && got.ThumbURL != "" && got.PreviewURL != ""
+	})
+
+	if err := st.photos.PermanentDelete(ctx, p.ID, user.ID); err != nil {
+		t.Fatalf("permanent delete: %v", err)
+	}
+	waitFor(t, "garbage collection", func() bool {
+		var n int
+		return st.db.QueryRowContext(ctx, `SELECT count(*) FROM objects`).Scan(&n) == nil && n == 0
+	})
+
+	// Stop the worker, then queue another upload whose variant job must survive
+	// the restart and be processed by a fresh worker over the same file.
+	cancel()
+	time.Sleep(50 * time.Millisecond)
+
+	p2, err := st.photos.Upload(ctx, photos.UploadInput{AlbumID: album.ID, UserID: user.ID, Filename: "b.png", Data: makePNG(t)})
+	if err != nil {
+		t.Fatalf("upload p2: %v", err)
+	}
+	got2, _ := st.photos.Get(ctx, p2.ID, user.ID)
+	if got2.PreviewURL != "" {
+		t.Fatalf("variants generated before restart")
+	}
+	closeDB()
+
+	st2, close2 := openStack(t, path, blobs)
+	defer close2()
+	worker2 := photos.NewWorker(st2.photos, 20*time.Millisecond, 10, time.Minute)
+	wctx2, cancel2 := context.WithCancel(ctx)
+	defer cancel2()
+	go worker2.Run(wctx2)
+
+	waitFor(t, "variants of second photo after restart", func() bool {
+		got, err := st2.photos.Get(ctx, p2.ID, user.ID)
+		return err == nil && got.ThumbURL != "" && got.PreviewURL != ""
+	})
+}
+
+func waitFor(t *testing.T, what string, cond func() bool) {
+	t.Helper()
+	deadline := time.Now().Add(10 * time.Second)
+	for time.Now().Before(deadline) {
+		if cond() {
+			return
+		}
+		time.Sleep(20 * time.Millisecond)
+	}
+	t.Fatalf("timed out waiting for %s", what)
+}