feat(api): implement notebook management CRUD endpoints

Implement Sprint 1: Notebook Management CRUD

- Add NotebookService with full CRUD operations
- Add POST /api/v1/notebooks (create notebook)
- Add GET /api/v1/notebooks (list with pagination)
- Add GET /api/v1/notebooks/{id} (get by ID)
- Add PATCH /api/v1/notebooks/{id} (partial update)
- Add DELETE /api/v1/notebooks/{id} (delete)
- Add Pydantic models for requests/responses
- Add custom exceptions (ValidationError, NotFoundError, NotebookLMError)
- Add comprehensive unit tests (31 tests, 97% coverage)
- Add API integration tests (26 tests)
- Fix router prefix duplication
- Fix JSON serialization in error responses

BREAKING CHANGE: None

.opencode/templates/architecture-adr.md

@@ -0,0 +1,29 @@
+# Architecture Decision Records
+
+> Registro delle decisioni architetturali e dei pattern di design utilizzati.
+
+## Formato
+
+```markdown
+## [YYYY-MM-DD] - [Titolo Decisione]
+
+### Contesto
+[Background e motivazione]
+
+### Decisione
+[Cosa è stato deciso]
+
+### Conseguenze
+- Positivo: [Benefici]
+- Negativo: [Trade-off]
+
+### Alternative Considerate
+- [Alternativa 1]: [Perché scartata]
+- [Alternativa 2]: [Perché scartata]
+```
+
+---
+
+## Decisions
+
+<!-- Aggiungere nuove decisioni qui in ordine cronologico crescente -->