test: remove tests that do not test behavior and strengthen weak ones

- Remove tests that only check markup, CSS, static text, wire:key strings,
  framework behavior, copied app logic, or expect(true)
- Replace source-grep and Reflection checks of security fixes with tests
  that run the real code (shell quoting, locked properties, 403 checks,
  webhook fork trust, log redaction, Sentinel token cleanup)
- Assert response bodies and unchanged data on API error paths
- Run the Traefik version job through handle() instead of private methods
- Update stale tests for scheduled task props, the default Postgres image,
  and the disabled transfer link of unvalidated servers

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/Unit/UpgradePostgresScriptTest.php

@@ -132,15 +132,3 @@ it('persists rollback metadata and exposes a rollback command', function () {
         ->toContain('rollback_postgres()')
         ->toContain('Rollback completed successfully.');
 });
-
-it('detects the active postgres volume instead of assuming coolify-db', function () {
-    $script = file_get_contents(getcwd().'/scripts/upgrade-postgres.sh');
-
-    expect($script)
-        ->toContain('current_postgres_mount_name()')
-        ->toContain('current_postgres_mount_path()')
-        ->toContain('current_postgres_image()')
-        ->toContain('Current active volume: ${PREVIOUS_VOLUME}')
-        ->toContain("Previous volume '")
-        ->toContain('will be kept for rollback');
-});