Add configuration for cron key and document code style conventions

- Added cron key to config.php for scheduled tasks.
- Created code_style_and_conventions.md to outline PHP version, file naming, DI pattern, controller wiring, Medoo ORM pitfalls, test conventions, caching, and database structure.
- Added project_overview.md detailing the purpose, tech stack, architecture, entry points, and key classes of the shopPRO project.
- Introduced suggested_commands.md for testing and system utilities commands.
- Added task_completion_checklist.md for a structured approach to completing tasks.
- Included .DS_Store files in autoload and templates directories for macOS compatibility.

.serena/memories/project_overview.md

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+# shopPRO — Project Overview
+
+## Purpose
+shopPRO is a PHP e-commerce platform with an admin panel, customer-facing storefront, and REST API.
+
+## Tech Stack
+- **Language**: PHP 7.4 (production runs PHP < 8.0 — do NOT use PHP 8.0+ syntax!)
+- **ORM**: Medoo (`$mdb` global, injected via DI in new code)
+- **Caching**: Redis via `\Shared\Cache\CacheHandler`
+- **Testing**: PHPUnit 9.6 via `phpunit.phar`
+- **Frontend**: Custom template engine (`\Shared\Tpl\Tpl`)
+- **Database**: MySQL with `pp_` table prefix
+- **Platform**: Windows (development), Linux (production)
+
+## PHP 7.4 Constraint — CRITICAL
+Do NOT use any PHP 8.0+ features:
+- No `match` expressions (use ternary/if-else)
+- No named arguments
+- No union types (`int|string`)
+- No `str_contains()`, `str_starts_with()`, `str_ends_with()`
+
+## Architecture
+Domain-Driven Design with Dependency Injection.
+
+### Layers
+1. **Domain** (`autoload/Domain/`) — Business logic repositories, 27 modules
+2. **Admin** (`autoload/admin/`) — Admin panel controllers, support, validation, view models
+3. **Frontend** (`autoload/front/`) — Customer-facing controllers and views
+4. **API** (`autoload/api/`) — REST API controllers
+5. **Shared** (`autoload/Shared/`) — Cache, Email, Helpers, Html, Image, Tpl
+
+### Domain Modules
+Article, Attribute, Banner, Basket, Cache, Category, Client, Coupon, Dashboard, Dictionaries, Integrations, Languages, Layouts, Newsletter, Order, Pages, PaymentMethod, Producer, Product, ProductSet, Promotion, Scontainers, Settings, ShopStatus, Transport, Update, User
+
+### Entry Points
+- `index.php` — Frontend
+- `admin/index.php` — Admin panel
+- `api.php` — REST API
+- `ajax.php` — Frontend AJAX
+- `admin/ajax.php` — Admin AJAX
+- `cron.php` — CRON jobs
+
+### Namespace Conventions (case-sensitive on Linux!)
+- `\Domain\` → `autoload/Domain/` (uppercase D)
+- `\admin\Controllers\` → `autoload/admin/Controllers/` (lowercase a)
+- `\Shared\` → `autoload/Shared/`
+- `\front\` → `autoload/front/`
+- `\api\` → `autoload/api/`
+
+### Autoloader
+Custom autoloader (not Composer at runtime). Tries:
+1. `autoload/{namespace}/class.{ClassName}.php` (legacy)
+2. `autoload/{namespace}/{ClassName}.php` (PSR-4 style)
+
+### Key Classes
+- `\admin\App` — Admin router
+- `\front\App` — Frontend router
+- `\front\LayoutEngine` — Frontend layout engine
+- `\Shared\Helpers\Helpers` — Utility methods
+- `\Shared\Tpl\Tpl` — Template engine
+- `\Shared\Cache\CacheHandler` — Redis cache
+- `\api\ApiRouter` — REST API router
+
+## Test Suite
+765 tests, 2153 assertions. Tests mirror source structure in `tests/Unit/`.