T03: plugin system framework + lifecycle + migrations + event bus + DI

- Plugin registry with discover/install/activate/deactivate/uninstall lifecycle
- PluginManifest Pydantic v2 schema (name, version, dependencies, routes, events, migrations)
- BasePlugin abstract class with lifecycle hooks (on_install/activate/deactivate/uninstall)
- Migration runner with tenant_id validator (rejects tables without tenant_id)
- Event bus integration: register/unregister listeners on activate/deactivate
- Service container DI: plugins receive db, cache, event_bus, storage, notifications
- Idempotent operations (activate active=200, deactivate inactive=200)
- UI registry for frontend component registration
- 47 new tests (14 ACs + 33 unit tests), 103 total tests pass
- Migration 0003: plugins + plugin_migrations tables
- Coverage: 85.92% for plugin modules

tests/conftest.py

@@ -32,6 +32,7 @@ from app.models.user import User, UserTenant
 from app.models.role import Role
 from app.models.company import Company
 from app.models.contact import Contact, CompanyContact
+from app.models.plugin import Plugin, PluginMigration
 from app.main import create_app
 
 
@@ -87,7 +88,7 @@ def clean_tables(db_setup):
     sync_eng = _get_sync_engine()
     with sync_eng.connect() as conn:
         # TRUNCATE all tables with CASCADE — fast and reliable isolation
-        conn.execute(text("TRUNCATE TABLE company_contacts, contacts, api_tokens, password_reset_tokens, notifications, deletion_log, audit_log, sessions, roles, companies, user_tenants, users, tenants CASCADE;"))
+        conn.execute(text("TRUNCATE TABLE plugin_migrations, plugins, company_contacts, contacts, api_tokens, password_reset_tokens, notifications, deletion_log, audit_log, sessions, roles, companies, user_tenants, users, tenants CASCADE;"))
         conn.commit()
     sync_eng.dispose()
     yield