Store mp3 size in database

Persist file size at creation and backfill missing sizes on list responses so the UI can display sizes reliably.

server/db.py

@@ -29,10 +29,17 @@ def init_db():
                     id SERIAL PRIMARY KEY,
                     text TEXT NOT NULL,
                     filename TEXT,
+                    size_bytes BIGINT,
                     created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
                 );
                 """
             )
+            cur.execute(
+                """
+                ALTER TABLE tts_items
+                ADD COLUMN IF NOT EXISTS size_bytes BIGINT;
+                """
+            )
             cur.execute(
                 """
                 CREATE INDEX IF NOT EXISTS tts_items_created_at_idx
@@ -72,12 +79,26 @@ def update_filename(tts_id: int, filename: str) -> None:
         conn.commit()
 
 
+def update_size_bytes(tts_id: int, size_bytes: int) -> None:
+    with get_conn() as conn:
+        with conn.cursor() as cur:
+            cur.execute(
+                """
+                UPDATE tts_items
+                SET size_bytes = %s
+                WHERE id = %s;
+                """,
+                (size_bytes, tts_id),
+            )
+        conn.commit()
+
+
 def list_items() -> List[Dict[str, Any]]:
     with get_conn() as conn:
         with conn.cursor(cursor_factory=psycopg2.extras.RealDictCursor) as cur:
             cur.execute(
                 """
-                SELECT id, created_at, filename
+                SELECT id, created_at, filename, size_bytes
                 FROM tts_items
                 ORDER BY created_at DESC;
                 """
@@ -91,7 +112,7 @@ def get_item(tts_id: int) -> Optional[Dict[str, Any]]:
         with conn.cursor(cursor_factory=psycopg2.extras.RealDictCursor) as cur:
             cur.execute(
                 """
-                SELECT id, text, filename, created_at
+                SELECT id, text, filename, size_bytes, created_at
                 FROM tts_items
                 WHERE id = %s;
                 """,