Refaktoryzacja Faza 0+1: PSR-4 autoloader + Shared/Domain klasy

- Dodano PSR-4 autoloader do wszystkich 6 punktów wejścia
- Shared\: CacheHandler, Helpers, Html, ImageManipulator, Tpl
- Domain\: LanguagesRepository, SettingsRepository, UserRepository
- Stare class.*.php → cienkie wrappery (kompatybilność wsteczna)
- Dodano dokumentację: docs/PROJECT_STRUCTURE.md + pozostałe docs/
- Dodano CLAUDE.md z workflow

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.serena/project.yml

@@ -115,3 +115,10 @@ initial_prompt: ""
 # override of the corresponding setting in serena_config.yml, see the documentation there.
 # If null or missing, the value from the global config is used.
 symbol_info_budget:
+
+# The language backend to use for this project.
+# If not set, the global setting from serena_config.yml is used.
+# Valid values: LSP, JetBrains
+# Note: the backend is fixed at startup. If a project with a different backend
+# is activated post-init, an error will be returned.
+language_backend: