Add basic logging to v0 Project API endpoints for improved observability

### Problem
The v0 Project API endpoints currently do not emit any logs. This makes it difficult to debug issues, understand request behavior, and diagnose failures or performance problems in production.

### Proposed Solution
Add minimal, structured logging to the following v0 Project API endpoints:
- list_projects
- get_project

The logs should capture:
- Request entry
- Successful completion
- Not-found cases (404)

### Scope
- Logging only (no behavior or API contract changes)
- No changes to authentication, routing, or operationId
- No sensitive information logged

### Benefits
- Improved debuggability and visibility into API usage
- Foundation for future observability, metrics, and tracing improvements
- No impact on existing API clients