fix(plugin): add version comparison and migration run on version mismatch

Bug 6: install() and activate() now compare the plugin's manifest
version with the stored DB version. If they differ, migrations are
re-run to bring the schema up to date and the DB version field is
updated. This ensures that updating a plugin with a new manifest
version triggers the migration runner automatically.

app/plugins/registry.py

@@ -211,12 +211,53 @@ class PluginRegistry:
                 )
         return warnings
 
+    # ── Version Comparison & Update Path ──
+
+    async def _check_and_run_version_migrations(
+        self, db: AsyncSession, name: str, record: PluginModel
+    ) -> bool:
+        """Compare manifest version with DB version and run migrations if different.
+
+        If the plugin's manifest version differs from the stored DB version,
+        re-run all migrations to bring the schema up to date, then update
+        the DB record's version field.
+
+        Returns True if migrations were run, False otherwise.
+        """
+        plugin = self.get_plugin(name)
+        if plugin is None:
+            return False
+
+        manifest_version = plugin.manifest.version
+        db_version = record.version
+
+        if manifest_version == db_version:
+            return False
+
+        logger.info(
+            f"Plugin '{name}' version mismatch: DB={db_version}, manifest={manifest_version}. "
+            f"Running migrations to update."
+        )
+
+        # Re-run migrations to apply any new migration files
+        if plugin.manifest.migrations:
+            await self.migration_runner.run_all_migrations(db, name, plugin.manifest.migrations)
+
+        # Update DB version to match manifest
+        record.version = manifest_version
+        await db.flush()
+        self._db_status[name] = record
+
+        logger.info(f"Plugin '{name}' updated to version {manifest_version}.")
+        return True
+
     # ── Install / Activate / Deactivate / Uninstall ──
 
     async def install(self, db: AsyncSession, name: str) -> PluginModel:
         """Install a plugin: run migrations and create DB record.
 
-        Idempotent: if already installed, returns existing record.
+        Idempotent: if already installed, checks for version updates and
+        returns existing record.
         Checks that all declared dependencies are installed first.
         """
         plugin = self.get_plugin(name)
@@ -226,6 +267,8 @@ class PluginRegistry:
         # Check if already installed in DB
         existing = await self._get_plugin_record(db, name)
         if existing is not None:
+            # Check for version update — run migrations if version changed
+            await self._check_and_run_version_migrations(db, name, existing)
             return existing
 
         # Check dependencies are installed
@@ -256,7 +299,8 @@ class PluginRegistry:
     async def activate(self, db: AsyncSession, name: str) -> PluginModel:
         """Activate a plugin: register routes, event listeners, set status=active.
 
-        Idempotent: if already active, returns existing record without error.
+        Idempotent: if already active, checks for version updates and
+        returns existing record without error.
         Checks that all declared dependencies are active first.
         Performs a soft permission check and logs warnings for unknown permissions.
         """
@@ -268,6 +312,9 @@ class PluginRegistry:
         if record is None:
             raise ValueError(f"Plugin '{name}' is not installed — install first")
 
+        # Check for version update — run migrations if version changed
+        await self._check_and_run_version_migrations(db, name, record)
+
         # Idempotent: already active
         if record.active and record.status == "active":
             return record