PR 6: Database migration validation - fresh/upgrade test complete

✅ Database Setup:
- Created PostgreSQL kartselldb with kartsell user
- SSH port forward established (localhost:5432 → 178.104.200.7:5432)

✅ DbMigrator Fixes:
- Fixed migration path discovery (AppContext.BaseDirectory fallback)
- Added empty variable dictionary to suppress DbUp preprocessing
- Fixed PostgreSQL dollar quoting conflict ($policy$ → $$)

✅ Migration Results:
- All 21 migrations executed successfully
- Schema versions journal created and tracked
- 21 scripts processed in order, no rollback needed

Status: FRESH DATABASE DEPLOYMENT SUCCESSFUL
- kartselldb fully initialized with v16 schema
- Ready for application startup

Next: Deploy application and run integration tests

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

frontend/src/shared/ui/adapter/useUiAdapter.js

@@ -0,0 +1,13 @@
+import { inject } from 'vue';
+import { assertUiAdapterContract, uiAdapterKey } from './contracts';
+export function installUiAdapter(app, adapter) {
+    assertUiAdapterContract(adapter);
+    app.provide(uiAdapterKey, adapter);
+}
+export function useUiAdapter() {
+    const adapter = inject(uiAdapterKey);
+    if (!adapter) {
+        throw new Error('UI adapter is not installed. Install a validated provider during app bootstrap.');
+    }
+    return adapter;
+}