Bump PHPStan to level 5 and fix type/annotation issues

[utkarshcloudinary]

Approach

• Bump PHPStan analysis to level 5 in phpstan.neon.dist.
• Fix all 61 resulting argument.type errors, which were all type mismatches at call sites:
  • Type casts at call sites for uniqid, esc_attr, gmdate, md5, substr, array_chunk, number_format_i18n, _n, filter_input results, and new Relationship.
  • Replaced null/false with array() for wp_register_script/wp_register_style/wp_enqueue_script $deps and Component::build_tag $attributes.
  • delete_metadata null object id changed to 0 (the WP delete-all pattern).
  • Widened docblocks where methods legitimately accept broader types: Media::cloudinary_url ($size/$transformations), Media::update_post_meta ($data → mixed), Api::upload/Api::url, Lock_File $file params, Component::get_part, and Sync_Queue::add_to_thread_queue.
  • Corrected wrong docblocks: Connect::validate_domain return type (bool → string|false), Delivery::set_usability filter docblocks (object → array), and Sync filter (WP_Post → \WP_Post|null).
  • Closure/local annotations: Admin::rest_save_settings filter closure now returns bool; added local @var Settings_Component[] in Plugin::setup_settings.
• No runtime behavior changes; all fixes are type coercions or annotation corrections.

QA notes

• Run vendor/bin/phpstan analyse --memory-limit=2G — should report No errors at level 5.
• Run PHP lint (composer lint) on the changed files — should pass with no PHPCS violations.
• Smoke test core flows (media upload/sync, delivery, admin settings, plan/usage UI) to confirm no regressions from the casts.