feat: Add repository guidelines for project structure, development commands, coding style, and testing

AGENTS.md

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+# Repository Guidelines
+
+## Project Structure & Module Organization
+BackPRO is a custom PHP MVC application (no Laravel/Symfony). Main code lives in `src/` under PSR-4 namespace `App\\`.
+- `src/Core/`: bootstrap, routing, base controller/model, config/auth helpers.
+- `src/Controllers/`, `src/Models/`, `src/Services/`: HTTP actions, data access, external integrations.
+- `templates/`: PHP view templates.
+- `config/routes.php`: all route definitions.
+- `cron/`: CLI jobs (`publish.php`, `semstorm.php`).
+- `migrations/`: ordered SQL schema changes (`001_*.sql`, `002_*.sql`, ...).
+- `assets/`: CSS/JS and WordPress theme files.
+- `storage/logs/`: runtime logs.
+
+## Build, Test, and Development Commands
+- `composer install`: install PHP dependencies.
+- `php -S localhost:8000 -t .`: run local dev server from repository root.
+- `php cron/publish.php`: run publishing workflow manually.
+- `php cron/semstorm.php`: sync SEO metrics manually.
+- `php -l src\\Services\\PublisherService.php`: lint a PHP file (repeat per changed file).
+
+## Coding Style & Naming Conventions
+- Target PHP `>=8.1` (see `composer.json`), use strict typing where applicable.
+- Follow PSR-4 and existing suffix patterns: `*Controller`, `*Service`, `*Model`.
+- Use 4-space indentation and braces/newline style consistent with `src/Core/App.php`.
+- Keep controllers thin; move API/business logic to `src/Services/`.
+- Escape output in templates (`htmlspecialchars`) and use prepared statements via PDO/model layer.
+
+## Testing Guidelines
+There is currently no dedicated `tests/` suite in this repository. For each change:
+- Lint modified PHP files with `php -l`.
+- Run affected flows through UI endpoints and/or cron scripts.
+- Verify database-impacting changes with the relevant migration and rollback plan.
+- Document manual test steps in the PR.
+
+## Commit & Pull Request Guidelines
+Git history favors Conventional Commit-style prefixes, especially `feat:` (for example: `feat: Integrate DataForSEO...`). Use:
+- `feat:`, `fix:`, `refactor:`, `docs:`, `chore:` with concise imperative summaries.
+- One logical change per commit; include migration changes in the same commit as dependent code.
+
+PRs should include:
+- Clear scope and risk summary.
+- Linked issue/task ID (if available).
+- Setup/migration notes (`migrations/00x_*.sql`, `.env` changes).
+- Screenshots for template/UI updates (`templates/`, `assets/`).