Add thumbnail support to Canvas and storage backends

Introduces a 'thumbnail' field to the Canvas model and updates all storage backends (AWS S3, filesystem, memory, and SQLite) to handle storing and retrieving this field. Also updates the API handler to accept and save the thumbnail, and switches SQLite driver to modernc.org/sqlite for improved compatibility. Updates .gitignore to exclude .db files.

stores/sqlite/store.go

@@ -9,9 +9,9 @@ import (
 	"log"
 	"time"
 
-	_ "github.com/mattn/go-sqlite3"
 	"github.com/oklog/ulid/v2"
 	"github.com/sirupsen/logrus"
+	_ "modernc.org/sqlite"
 )
 
 type sqliteStore struct {
@@ -20,7 +20,7 @@ type sqliteStore struct {
 
 // NewStore creates a new SQLite-based store.
 func NewStore(dataSourceName string) *sqliteStore {
-	db, err := sql.Open("sqlite3", dataSourceName)
+	db, err := sql.Open("sqlite", dataSourceName)
 	if err != nil {
 		log.Fatalf("failed to open sqlite database: %v", err)
 	}
@@ -37,6 +37,7 @@ func NewStore(dataSourceName string) *sqliteStore {
 		id TEXT NOT NULL,
 		user_id TEXT NOT NULL,
 		name TEXT,
+		thumbnail TEXT,
 		data BLOB,
 		created_at DATETIME,
 		updated_at DATETIME,
@@ -89,7 +90,7 @@ func (s *sqliteStore) Create(ctx context.Context, document *core.Document) (stri
 
 // CanvasStore implementation
 func (s *sqliteStore) List(ctx context.Context, userID string) ([]*core.Canvas, error) {
-	rows, err := s.db.QueryContext(ctx, "SELECT id, name, updated_at FROM canvases WHERE user_id = ?", userID)
+	rows, err := s.db.QueryContext(ctx, "SELECT id, name, updated_at, thumbnail FROM canvases WHERE user_id = ?", userID)
 	if err != nil {
 		return nil, err
 	}
@@ -99,7 +100,7 @@ func (s *sqliteStore) List(ctx context.Context, userID string) ([]*core.Canvas,
 	for rows.Next() {
 		var canvas core.Canvas
 		canvas.UserID = userID
-		if err := rows.Scan(&canvas.ID, &canvas.Name, &canvas.UpdatedAt); err != nil {
+		if err := rows.Scan(&canvas.ID, &canvas.Name, &canvas.UpdatedAt, &canvas.Thumbnail); err != nil {
 			return nil, err
 		}
 		canvases = append(canvases, &canvas)
@@ -111,7 +112,7 @@ func (s *sqliteStore) Get(ctx context.Context, userID, id string) (*core.Canvas,
 	var canvas core.Canvas
 	canvas.UserID = userID
 	canvas.ID = id
-	err := s.db.QueryRowContext(ctx, "SELECT name, data, created_at, updated_at FROM canvases WHERE user_id = ? AND id = ?", userID, id).Scan(&canvas.Name, &canvas.Data, &canvas.CreatedAt, &canvas.UpdatedAt)
+	err := s.db.QueryRowContext(ctx, "SELECT name, data, created_at, updated_at, thumbnail FROM canvases WHERE user_id = ? AND id = ?", userID, id).Scan(&canvas.Name, &canvas.Data, &canvas.CreatedAt, &canvas.UpdatedAt, &canvas.Thumbnail)
 	if err != nil {
 		if err == sql.ErrNoRows {
 			return nil, fmt.Errorf("canvas not found")
@@ -138,10 +139,10 @@ func (s *sqliteStore) Save(ctx context.Context, canvas *core.Canvas) error {
 
 	if exists {
 		// Update
-		_, err = tx.ExecContext(ctx, "UPDATE canvases SET name = ?, data = ?, updated_at = ? WHERE user_id = ? AND id = ?", canvas.Name, canvas.Data, now, canvas.UserID, canvas.ID)
+		_, err = tx.ExecContext(ctx, "UPDATE canvases SET name = ?, data = ?, updated_at = ?, thumbnail = ? WHERE user_id = ? AND id = ?", canvas.Name, canvas.Data, now, canvas.Thumbnail, canvas.UserID, canvas.ID)
 	} else {
 		// Insert
-		_, err = tx.ExecContext(ctx, "INSERT INTO canvases (id, user_id, name, data, created_at, updated_at) VALUES (?, ?, ?, ?, ?, ?)", canvas.ID, canvas.UserID, canvas.Name, canvas.Data, now, now)
+		_, err = tx.ExecContext(ctx, "INSERT INTO canvases (id, user_id, name, data, created_at, updated_at, thumbnail) VALUES (?, ?, ?, ?, ?, ?, ?)", canvas.ID, canvas.UserID, canvas.Name, canvas.Data, now, now, canvas.Thumbnail)
 	}
 
 	if err != nil {