Make migrations more better

app/migrations/__init__.py

@@ -0,0 +1,66 @@
+"""
+Database migrations using SQLite's user_version pragma.
+
+Migrations run automatically on startup. The user_version pragma tracks
+which migrations have been applied (defaults to 0 for existing databases).
+
+Each migration lives in its own file: ``_NNN_description.py``, exposing an
+``async def migrate(conn)`` entry point.  The runner auto-discovers files by
+numeric prefix and executes them in order.
+
+This approach is safe for existing users - their databases have user_version=0,
+so all migrations run in order on first startup after upgrade.
+"""
+
+import importlib
+import logging
+import pkgutil
+import re
+
+import aiosqlite
+
+logger = logging.getLogger(__name__)
+
+
+async def get_version(conn: aiosqlite.Connection) -> int:
+    """Get current schema version from SQLite user_version pragma."""
+    cursor = await conn.execute("PRAGMA user_version")
+    row = await cursor.fetchone()
+    return row[0] if row else 0
+
+
+async def set_version(conn: aiosqlite.Connection, version: int) -> None:
+    """Set schema version using SQLite user_version pragma."""
+    await conn.execute(f"PRAGMA user_version = {version}")
+
+
+async def run_migrations(conn: aiosqlite.Connection) -> int:
+    """
+    Run all pending migrations.
+
+    Returns the number of migrations applied.
+    """
+    version = await get_version(conn)
+    applied = 0
+
+    for module_info in sorted(pkgutil.iter_modules(__path__), key=lambda m: m.name):
+        match = re.match(r"_(\d+)_", module_info.name)
+        if not match:
+            continue
+        num = int(match.group(1))
+        if num <= version:
+            continue
+        logger.info("Applying migration %d: %s", num, module_info.name)
+        mod = importlib.import_module(f"{__name__}.{module_info.name}")
+        await mod.migrate(conn)
+        await set_version(conn, num)
+        applied += 1
+
+    if applied > 0:
+        logger.info(
+            "Applied %d migration(s), schema now at version %d", applied, await get_version(conn)
+        )
+    else:
+        logger.debug("Schema up to date at version %d", version)
+
+    return applied