feat: Remove global db.Dbpool with dependency injection (Phase 0)

- Add Database struct in internal/db/database.go with Pool, Ctx, and RunMigrations()
- Update server.go to use Database struct with NewServerInstance()
- Add backend.go with InitBackend(), BackendRepo(), BackendCtx(), BackendPool()
- Update music.go and sync.go to use BackendRepo() and BackendCtx() instead of db.Dbpool/db.Ctx
- Update token_handler.go to accept pool parameter
- Update routes.go to use s.db.Pool for middleware
- Update cmd/main.go to use NewServerInstance() and HTTPServer()
- Update test_helpers.go to initialize backend with test database
- Update test files to use backend.BackendPool() and backend.BackendCtx()

Benefits:
- Easier to mock database for unit tests
- Follows Go best practices (dependency injection)
- Better architecture with explicit dependencies
- RunMigrations() replaces old Migrate_db() function

Note: Global db.Dbpool and db.Ctx still exist in dbHelper.go for backward compatibility
with test_helpers.go, but production code no longer uses them.

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

internal/backend/sync.go

@@ -7,7 +7,6 @@ import (
 	"fmt"
 	"io"
 	"io/fs"
-	"music-server/internal/db"
 	"music-server/internal/db/repository"
 	"music-server/internal/logging"
 	"os"
@@ -80,8 +79,8 @@ func (gs GameStatus) String() string {
 }
 
 func ResetDB() {
-	repo.ClearSongs(db.Ctx)
-	repo.ClearGames(db.Ctx)
+	repo.ClearSongs(BackendCtx())
+	repo.ClearGames(BackendCtx())
 }
 
 func SyncProgress() ProgressResponse {
@@ -206,13 +205,13 @@ func syncGamesNew(full bool) {
 	catchedErrors = nil
 	brokenSongs = nil
 
-	gamesBeforeSync, err = repo.FindAllGames(db.Ctx)
+	gamesBeforeSync, err = repo.FindAllGames(BackendCtx())
 	handleError("FindAllGames Before", err, "")
 	logging.GetLogger().Info("Starting sync", zap.Int("games_before", len(gamesBeforeSync)))
 
-	allGames, err = repo.GetAllGamesIncludingDeleted(db.Ctx)
+	allGames, err = repo.GetAllGamesIncludingDeleted(BackendCtx())
 	handleError("GetAllGamesIncludingDeleted", err, "")
-	err = repo.SetGameDeletionDate(db.Ctx)
+	err = repo.SetGameDeletionDate(BackendCtx())
 	handleError("SetGameDeletionDate", err, "")
 
 	directories, err := os.ReadDir(musicPath)
@@ -237,7 +236,7 @@ func syncGamesNew(full bool) {
 	syncWg.Wait()
 	checkBrokenSongsNew()
 
-	gamesAfterSync, err = repo.FindAllGames(db.Ctx)
+	gamesAfterSync, err = repo.FindAllGames(BackendCtx())
 	handleError("FindAllGames After", err, "")
 
 	finished := time.Now()
@@ -249,7 +248,7 @@ func syncGamesNew(full bool) {
 }
 
 func checkBrokenSongsNew() {
-	allSongs, err := repo.FetchAllSongs(db.Ctx)
+	allSongs, err := repo.FetchAllSongs(BackendCtx())
 	handleError("FetchAllSongs", err, "")
 	var brokenWg sync.WaitGroup
 	poolBroken, _ := ants.NewPool(200, ants.WithPreAlloc(true))
@@ -263,7 +262,7 @@ func checkBrokenSongsNew() {
 		})
 	}
 	brokenWg.Wait()
-	err = repo.RemoveBrokenSongs(db.Ctx, brokenSongs)
+	err = repo.RemoveBrokenSongs(BackendCtx(), brokenSongs)
 	handleError("RemoveBrokenSongs", err, "")
 }
 
@@ -336,7 +335,7 @@ func syncGameNew(file os.DirEntry, foldersToSkip []string, baseDir string, full
 						break
 					}
 				}
-				err = repo.InsertGameWithExistingId(db.Ctx, repository.InsertGameWithExistingIdParams{ID: id, GameName: file.Name(), Path: gameDir, Hash: dirHash})
+				err = repo.InsertGameWithExistingId(BackendCtx(), repository.InsertGameWithExistingIdParams{ID: id, GameName: file.Name(), Path: gameDir, Hash: dirHash})
 				handleError("InsertGameWithExistingId", err, "")
 				if err != nil {
 					logging.GetLogger().Debug("Game already exists, removing old ID file",
@@ -370,7 +369,7 @@ func syncGameNew(file os.DirEntry, foldersToSkip []string, baseDir string, full
 				zap.String("game", file.Name()),
 				zap.String("hash", dirHash),
 				zap.String("status", status.String()))
-			err = repo.UpdateGameHash(db.Ctx, repository.UpdateGameHashParams{Hash: dirHash, ID: id})
+			err = repo.UpdateGameHash(BackendCtx(), repository.UpdateGameHashParams{Hash: dirHash, ID: id})
 			handleError("UpdateGameHash", err, "")
 			gamesChangedContent = append(gamesChangedContent, file.Name())
 			newCheckSongs(entries, gameDir, id)
@@ -381,7 +380,7 @@ func syncGameNew(file os.DirEntry, foldersToSkip []string, baseDir string, full
 				zap.String("newName", file.Name()),
 				zap.String("hash", dirHash),
 				zap.String("status", status.String()))
-			err = repo.UpdateGameName(db.Ctx, repository.UpdateGameNameParams{Name: file.Name(), Path: gameDir, ID: id})
+			err = repo.UpdateGameName(BackendCtx(), repository.UpdateGameNameParams{Name: file.Name(), Path: gameDir, ID: id})
 			handleError("UpdateGameName", err, "")
 			newCheckSongs(entries, gameDir, id)
 			if gamesChangedTitle == nil {
@@ -416,7 +415,7 @@ func syncGameNew(file os.DirEntry, foldersToSkip []string, baseDir string, full
 			zap.String("game", file.Name()),
 			zap.String("hash", dirHash),
 			zap.String("status", status.String()))
-		err = repo.RemoveDeletionDate(db.Ctx, id)
+		err = repo.RemoveDeletionDate(BackendCtx(), id)
 		handleError("RemoveDeletionDate", err, "")
 	}
 	foldersSynced++
@@ -428,13 +427,13 @@ func syncGameNew(file os.DirEntry, foldersToSkip []string, baseDir string, full
 
 func insertGameNew(name string, path string, hash string) int32 {
 	var duplicateError = errors.New("ERROR: duplicate key value violates unique")
-	id, err := repo.InsertGame(db.Ctx, repository.InsertGameParams{GameName: name, Path: path, Hash: hash})
+	id, err := repo.InsertGame(BackendCtx(), repository.InsertGameParams{GameName: name, Path: path, Hash: hash})
 	handleError("InsertGame", err, "")
 	if err != nil {
 		logging.GetLogger().Warn("ID collision detected, resetting sequence")
 		if strings.HasPrefix(err.Error(), duplicateError.Error()) {
 			logging.GetLogger().Debug("Resetting game ID sequence")
-			_, err = repo.ResetGameIdSeq(db.Ctx)
+			_, err = repo.ResetGameIdSeq(BackendCtx())
 			handleError("ResetGameIdSeq", err, "")
 			id = insertGameNew(name, path, hash)
 		}
@@ -478,7 +477,7 @@ func newCheckSong(entry os.DirEntry, gameDir string, id int32) bool {
 		fileName := entry.Name()
 		songName, _ := strings.CutSuffix(fileName, ".mp3")
 
-		song, err := repo.GetSongWithHash(db.Ctx, songHash)
+		song, err := repo.GetSongWithHash(BackendCtx(), songHash)
 		handleError("GetSongWithHash", err, fmt.Sprintf("GameID: %d | Path: %s | SongName: %s | SongHash: %s", id, path, entry.Name(), songHash))
 		if err == nil {
 			if song.SongName == songName && song.Path == path {
@@ -491,31 +490,31 @@ func newCheckSong(entry os.DirEntry, gameDir string, id int32) bool {
 			zap.String("song_name", songName),
 			zap.String("song_hash", songHash))
 
-		count, err := repo.CheckSongWithHash(db.Ctx, songHash)
+		count, err := repo.CheckSongWithHash(BackendCtx(), songHash)
 		handleError("CheckSongWithHash", err, fmt.Sprintf("GameID: %d | Path: %s | SongName: %s | SongHash: %s\n", id, path, entry.Name(), songHash))
 		if err != nil {
-			count2, err := repo.CheckSong(db.Ctx, path)
+			count2, err := repo.CheckSong(BackendCtx(), path)
 			handleError("CheckSong", err, fmt.Sprintf("GameID: %d | Path: %s | SongName: %s | SongHash: %s\n", id, path, entry.Name(), songHash))
 			if count2 > 0 {
-				err = repo.AddHashToSong(db.Ctx, repository.AddHashToSongParams{Hash: songHash, Path: path})
+				err = repo.AddHashToSong(BackendCtx(), repository.AddHashToSongParams{Hash: songHash, Path: path})
 				handleError("AddHashToSong", err, fmt.Sprintf("GameID: %d | Path: %s | SongName: %s | SongHash: %s", id, path, entry.Name(), songHash))
-				count, err = repo.CheckSongWithHash(db.Ctx, songHash)
+				count, err = repo.CheckSongWithHash(BackendCtx(), songHash)
 				handleError("CheckSongWithHash 2", err, fmt.Sprintf("GameID: %d | Path: %s | SongName: %s | SongHash: %s", id, path, entry.Name(), songHash))
 			}
 		}
 
 		//count, _ := repo.CheckSong(ctx, path)
 		if count > 0 {
-			err = repo.UpdateSong(db.Ctx, repository.UpdateSongParams{SongName: songName, FileName: &fileName, Path: path, Hash: songHash})
+			err = repo.UpdateSong(BackendCtx(), repository.UpdateSongParams{SongName: songName, FileName: &fileName, Path: path, Hash: songHash})
 			handleError("UpdateSong", err, fmt.Sprintf("GameID: %d | Path: %s | SongName: %s | SongHash: %s", id, path, entry.Name(), songHash))
 		} else {
-			count2, err := repo.CheckSong(db.Ctx, path)
+			count2, err := repo.CheckSong(BackendCtx(), path)
 			handleError("CheckSong", err, fmt.Sprintf("GameID: %d | Path: %s | SongName: %s | SongHash: %s", id, path, entry.Name(), songHash))
 			if count2 > 0 {
-				err = repo.AddHashToSong(db.Ctx, repository.AddHashToSongParams{Hash: songHash, Path: path})
+				err = repo.AddHashToSong(BackendCtx(), repository.AddHashToSongParams{Hash: songHash, Path: path})
 				handleError("AddHashToSong", err, fmt.Sprintf("GameID: %d | Path: %s | SongName: %s | SongHash: %s", id, path, entry.Name(), songHash))
 			} else {
-				err = repo.AddSong(db.Ctx, repository.AddSongParams{GameID: id, SongName: songName, Path: path, FileName: &fileName, Hash: songHash})
+				err = repo.AddSong(BackendCtx(), repository.AddSongParams{GameID: id, SongName: songName, Path: path, FileName: &fileName, Hash: songHash})
 				handleError("AddSong", err, fmt.Sprintf("GameID: %d | Path: %s | SongName: %s | SongHash: %s", id, path, entry.Name(), songHash))
 
 			}