feat(maker): AI parsing schede tecniche PDF via OpenRouter

- Nuovo servizio ai_service.py: estrae testo da PDF (pdfplumber) + analisi AI (OpenRouter)
- Endpoint POST /api/recipes/{id}/parse-technical-sheet con validazione file
- UI: bottone "Importa da PDF" nel task editor con modale upload + preview editabile
- Task suggeriti modificabili/rimovibili prima della creazione bulk
- Config: OPENROUTER_API_KEY e OPENROUTER_MODEL in .env
- Dipendenze: pdfplumber + httpx aggiunti a server deps

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/backend/config.py

@@ -34,6 +34,10 @@ class Settings(BaseSettings):
     # Setup page (empty = disabled)
     setup_password: str | None = None
 
+    # AI / OpenRouter (for technical sheet parsing)
+    openrouter_api_key: str | None = None
+    openrouter_model: str = "anthropic/claude-sonnet-4"
+
     @property
     def database_url(self) -> str:
         """Async MySQL connection string."""