docs(06-03): add SAFETY comments to all 12 hand-crafted SQL statements

- 7 SAFETY comments in search.go (FTS5 MATCH/INSERT/DELETE operations)
- 3 SAFETY comments in library.go (FTS5 INSERT/DELETE in commitNewAudioFile, updateAudioFileMetadata)
- 1 SAFETY comment in rescan.go (FTS5 DELETE in clearAllLibraryData)
- 1 SAFETY comment in persistence.go (variable-count multi-row INSERT)
- Cross-references link library.go/rescan.go back to search.go
- Two-part format: why sqlc can't handle it + what makes it safe

backend/database/search.go

@@ -31,6 +31,7 @@ func (d *DB) SearchFTS(
 	// special characters are treated as literals.
 	ftsQuery := buildFTSQuery(query)
 
+	// SAFETY: FTS5 MATCH syntax unsupported by sqlc. Query is parameterized; no string interpolation.
 	rows, err := d.db.QueryContext(d.Ctx, `
 		SELECT
 			tm.file_path,
@@ -77,6 +78,7 @@ func (d *DB) SearchFTSByFilename(
 	ftsQuery := "file_path : " +
 		strings.Join(tokens, " ")
 
+	// SAFETY: FTS5 MATCH syntax unsupported by sqlc. Query is parameterized; no string interpolation.
 	rows, err := d.db.QueryContext(d.Ctx, `
 		SELECT
 			tm.file_path,
@@ -106,6 +108,7 @@ func (d *DB) InsertSearchIndex(
 	rowid int64,
 	filePath, title, artist, album string,
 ) error {
+	// SAFETY: FTS5 virtual table INSERT unsupported by sqlc. All values are parameterized.
 	_, err := d.db.ExecContext(d.Ctx, `
 		INSERT INTO search_index(rowid, file_path, title, artist, album)
 		VALUES (?, ?, ?, ?, ?)
@@ -116,6 +119,7 @@ func (d *DB) InsertSearchIndex(
 
 // DeleteSearchIndex removes a row from the FTS5 search_index.
 func (d *DB) DeleteSearchIndex(rowid int64) error {
+	// SAFETY: FTS5 virtual table DELETE unsupported by sqlc. Rowid is parameterized.
 	_, err := d.db.ExecContext(d.Ctx, `
 		DELETE FROM search_index WHERE rowid = ?
 	`, rowid)
@@ -125,6 +129,7 @@ func (d *DB) DeleteSearchIndex(rowid int64) error {
 
 // ClearSearchIndex removes all rows from the FTS5 search_index.
 func (d *DB) ClearSearchIndex() error {
+	// SAFETY: FTS5 virtual table DELETE unsupported by sqlc. No parameters; unconditional delete.
 	_, err := d.db.ExecContext(d.Ctx, `
 		DELETE FROM search_index
 	`)
@@ -141,6 +146,7 @@ func (d *DB) RebuildSearchIndex() error {
 		)
 	}
 
+	// SAFETY: FTS5 virtual table INSERT unsupported by sqlc. All values sourced from track_metadata VIEW; no user input.
 	_, err := d.db.ExecContext(d.Ctx, `
 		INSERT INTO search_index(rowid, file_path, title, artist, album)
 		SELECT id, file_path, title, artist_name, album
@@ -189,6 +195,7 @@ func (d *DB) SearchFTSTracks(
 
 	ftsQuery := buildFTSQuery(query)
 
+	// SAFETY: FTS5 MATCH syntax unsupported by sqlc. Query is parameterized; no string interpolation.
 	rows, err := d.db.QueryContext(d.Ctx, `
 		SELECT
 			tm.file_path,

backend/library/library.go

@@ -793,6 +793,7 @@ func (l *Library) saveAudioFile(
 
 	album := tags.Album
 
+	// SAFETY: FTS5 virtual table, see search.go:InsertSearchIndex. All values parameterized.
 	if _, err := tx.ExecContext(
 		l.ctx,
 		`INSERT INTO search_index(rowid, file_path, title, artist, album)
@@ -874,6 +875,7 @@ func (l *Library) updateAudioFileMetadata(
 
 	album := tags.Album
 
+	// SAFETY: FTS5 virtual table, see search.go:DeleteSearchIndex. Rowid parameterized.
 	if _, err := tx.ExecContext(
 		l.ctx,
 		`DELETE FROM search_index WHERE rowid = ?`,
@@ -888,6 +890,7 @@ func (l *Library) updateAudioFileMetadata(
 		metrics.addWarning(result.absolutePath, "commit", err)
 	}
 
+	// SAFETY: FTS5 virtual table, see search.go:InsertSearchIndex. All values parameterized.
 	if _, err := tx.ExecContext(
 		l.ctx,
 		`INSERT INTO search_index(rowid, file_path, title, artist, album)

backend/library/rescan.go

@@ -161,6 +161,7 @@ func (l *Library) clearLibraryTables() error {
 	}
 
 	// Clear FTS5 search index.
+	// SAFETY: FTS5 virtual table, see search.go:ClearSearchIndex. No parameters; unconditional delete.
 	if _, err := tx.ExecContext(
 		l.ctx, `DELETE FROM search_index`,
 	); err != nil {

backend/queue/persistence.go

@@ -151,6 +151,7 @@ func (q *Queue) insertTrackBatch(tx *sql.Tx, batch []Track) error {
 		args = append(args, track.AudioFileID, track.Position)
 	}
 
+	// SAFETY: Multi-row INSERT with variable row count unsupported by sqlc. Placeholder count matches args length; no string interpolation.
 	query := "INSERT INTO queue_tracks (audio_file_id, position) VALUES " +
 		strings.Join(valuePlaceholders, ",")