chore: remove IS_APPLICATION_ENABLED feature flag (#19081)

## Summary
- Remove the `IS_APPLICATION_ENABLED` feature flag — application
features are now always enabled
- Remove `@RequireFeatureFlag` decorators and `FeatureFlagGuard` from 7
application resolvers (registration, development, manifest, install,
upgrade, marketplace, oauth)
- Remove frontend feature flag checks: settings navigation visibility,
route protection wrapper, side panel widget type gating, and role
permission flag filtering
- Delete the integration test for disabled-flag behavior
- Clean up seed data, test mocks, and generated schema files

packages/twenty-server/src/engine/twenty-orm/entity-manager/workspace-entity-manager.spec.ts

@@ -233,7 +233,6 @@ describe('WorkspaceEntityManager', () => {
         IS_UNIQUE_INDEXES_ENABLED: false,
         IS_JSON_FILTER_ENABLED: false,
         IS_AI_ENABLED: false,
-        IS_APPLICATION_ENABLED: false,
         IS_MARKETPLACE_ENABLED: false,
         IS_RECORD_PAGE_LAYOUT_EDITING_ENABLED: false,
         IS_PUBLIC_DOMAIN_ENABLED: false,
@@ -273,7 +272,6 @@ describe('WorkspaceEntityManager', () => {
         IS_UNIQUE_INDEXES_ENABLED: false,
         IS_JSON_FILTER_ENABLED: false,
         IS_AI_ENABLED: false,
-        IS_APPLICATION_ENABLED: false,
         IS_PUBLIC_DOMAIN_ENABLED: false,
         IS_EMAILING_DOMAIN_ENABLED: false,
         IS_ROW_LEVEL_PERMISSION_PREDICATES_ENABLED: false,