Fix 10 critical/high issues from Phase 6-7 audit ...

- Entity::select_from_db() throws on missing record (fatal error fix)
- Scripts::select_scripts_by_aliases_types() early return on empty array (SQL syntax fix)
- ThinBuilder WHERE operator whitelist (SQL injection prevention)
- validate_identifier() rejects numeric start (SQL correctness)
- Remove escape_string_in_arr() dead code (security hygiene)
- MetaManager::create_or_update() wrapped in transaction (race condition)
- Scripts::remove_scope() deletes DB before file (consistency)
- IN clause guards against non-array values (PHP 8 TypeError fix)
- Short where syntax supports IN operator (correctness)
- DeviceAuth::kill() clears Device auth cache (stale data fix)

Add high-complexity PHPUnit tests: retry/backoff, auth guard, transactions, happy-paths, script state ...

- Refactor Base.php: extract executeCurl/getCurlInfo for mockability
- Refactor App.php: split api_auth_guard into check_api_auth (testable) + guard wrapper
- Refactor Devices.php: add optional ?Base DI to connect_new_device
- Update TestApp.php: add control_scripts_instances for script tests
- Update bootstrap.php: define PHPUNIT_TEST to skip new App() autoload side-effect

New test files:
- DeviceAPIBaseRetryTest (7 tests) — retry/backoff with mock cURL
- AppAuthGuardTest (7 tests) — auth + rate limiter without exit
- DevicesModelTransactionTest (4 tests) — happy path, rollback, mode checks
- AreasControllerHappyPathTest (7 tests) — full area CRUD success flows
- ScriptsModelStateTest (8 tests) — scope list, script state, enable/disable

Total: 113 tests, 285 assertions — all passing.