docs: map existing codebase

- stack.md (68 lines) - PHP/MySQL/Apache stack, vendored libraries
- architecture.md (131 lines) - Custom MVC CMS, dual-layer (front/admin)
- structure.md (170 lines) - Directory layout and conventions
- conventions.md (98 lines) - PHP snake_case, SCSS $c/$f prefixes, jQuery patterns
- testing.md (49 lines) - No automated tests detected
- integrations.md (111 lines) - Google Maps, PHPMailer, Pixieset, Facebook
- concerns.md (150 lines) - Critical security issues: hardcoded creds, MD5, unserialize
- db_schema.md (260 lines) - ~32 tables with pp_ prefix, inferred from source
- tech_changelog.md (9 lines) - Initial log entry

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

.paul/codebase/tech_changelog.md

@@ -0,0 +1,14 @@
+# Technical Changelog
+
+> Chronological log of technical changes — what and why.
+
+## 2026-05-05 — Codebase Mapping
+
+**Co zrobiono / What changed:**
+- Initial codebase map created in `.paul/codebase/` (9 documents)
+- Analyzed stack, architecture, structure, conventions, integrations, concerns, DB schema
+
+**Dlaczego / Why:**
+- First-time PAUL project setup — baseline documentation for future planning
+
+---