refactor: remove test.db, use only posterg.db for all environments

- Simplified Database.php determineDatabasePath to always use posterg.db
- Removed test.db auto-detection based on php_sapi_name
- Removed test.db targets from justfile (migrate-test removed)
- Removed CreateTestDatabase.php fixture script
- Updated migrate.sh to only init posterg.db
- Updated setup-dev.sh to init posterg.db
- Updated run-tests.php (removed DB_ENV=test env var)
- Updated deploy-db to use posterg.db
- Removed test.db file

refactor: remove empty fixtures directory

app/storage/README.md

@@ -188,25 +188,9 @@ Query `v_theses_public` view with filters:
 ## 🛠️ Development Workflow
 
 ### Local Development
-1. Use `test.db` for development
-2. Create via `just init-test-db`
-3. Populate with `just create-fixtures`
-4. Test queries before deployment
-
-### Schema Changes
-1. Update `schema.sql`
-2. Update `DATABASE_SPECIFICATION.md`
-3. Test on `test.db`
-4. Deploy to production (manual migration)
-
-### Testing
-```bash
-# Run tests on local database
-just test-public-all
-
-# Check database stats
-just stats-public
-```
+1. Use `posterg.db` for development
+2. Create via `just init-db`
+3. Test queries before deployment
 
 ## 📞 Need Help?