fix(db,downloader): fix server error on upgrade from 3.1.x to 3.2.x (#956)

- Fix 'dict' object has no attribute 'files' in renamer by using dict
  access for qBittorrent API responses and fetching file lists via
  separate torrents/files endpoint
- Replace version-file-based migration with schema_version table to
  reliably track and apply database migrations on every startup
- Add air_weekday column migration as versioned migration entry
- Add torrents_files method to QbDownloader and Aria2Downloader

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

backend/src/module/database/combine.py

@@ -14,6 +14,20 @@ from .user import UserDatabase
 
 logger = logging.getLogger(__name__)
 
+# Increment this when adding new migrations to MIGRATIONS list.
+CURRENT_SCHEMA_VERSION = 1
+
+# Each migration is a tuple of (version, description, list of SQL statements).
+# Migrations are applied in order. A migration at index i brings the schema
+# from version i to version i+1.
+MIGRATIONS = [
+    (
+        1,
+        "add air_weekday column to bangumi",
+        ["ALTER TABLE bangumi ADD COLUMN air_weekday INTEGER"],
+    ),
+]
+
 
 class Database(Session):
     def __init__(self, engine=e):
@@ -26,20 +40,64 @@ class Database(Session):
 
     def create_table(self):
         SQLModel.metadata.create_all(self.engine)
-        self._migrate_columns()
+        self._ensure_schema_version_table()
 
-    def _migrate_columns(self):
-        """Add new columns to existing tables if they don't exist."""
+    def _ensure_schema_version_table(self):
+        """Create the schema_version table if it doesn't exist."""
+        with self.engine.connect() as conn:
+            conn.execute(text(
+                "CREATE TABLE IF NOT EXISTS schema_version ("
+                "  id INTEGER PRIMARY KEY,"
+                "  version INTEGER NOT NULL"
+                ")"
+            ))
+            conn.commit()
+
+    def _get_schema_version(self) -> int:
+        """Get the current schema version from the database."""
         inspector = inspect(self.engine)
-        if "bangumi" in inspector.get_table_names():
-            columns = [col["name"] for col in inspector.get_columns("bangumi")]
-            if "air_weekday" not in columns:
+        if "schema_version" not in inspector.get_table_names():
+            return 0
+        with self.engine.connect() as conn:
+            result = conn.execute(text("SELECT version FROM schema_version WHERE id = 1"))
+            row = result.fetchone()
+            return row[0] if row else 0
+
+    def _set_schema_version(self, version: int):
+        """Update the schema version in the database."""
+        with self.engine.connect() as conn:
+            conn.execute(text(
+                "INSERT OR REPLACE INTO schema_version (id, version) VALUES (1, :version)"
+            ), {"version": version})
+            conn.commit()
+
+    def run_migrations(self):
+        """Run pending schema migrations based on the stored schema version."""
+        self._ensure_schema_version_table()
+        current = self._get_schema_version()
+        if current >= CURRENT_SCHEMA_VERSION:
+            return
+        inspector = inspect(self.engine)
+        tables = inspector.get_table_names()
+        for version, description, statements in MIGRATIONS:
+            if version <= current:
+                continue
+            # Check if migration is actually needed (column may already exist)
+            needs_run = True
+            if "bangumi" in tables and version == 1:
+                columns = [col["name"] for col in inspector.get_columns("bangumi")]
+                if "air_weekday" in columns:
+                    needs_run = False
+            if needs_run:
                 with self.engine.connect() as conn:
-                    conn.execute(
-                        text("ALTER TABLE bangumi ADD COLUMN air_weekday INTEGER")
-                    )
+                    for stmt in statements:
+                        conn.execute(text(stmt))
                     conn.commit()
-                logger.info("[Database] Migrated: added air_weekday column to bangumi table.")
+                logger.info(f"[Database] Migration v{version}: {description}")
+            else:
+                logger.debug(f"[Database] Migration v{version} skipped (already applied): {description}")
+        self._set_schema_version(CURRENT_SCHEMA_VERSION)
+        logger.info(f"[Database] Schema version is now {CURRENT_SCHEMA_VERSION}.")
 
     def drop_table(self):
         SQLModel.metadata.drop_all(self.engine)