Remove sensitive logging from todo APIs

**Description**
**CRITICAL**: Todo API handlers log request headers and token-related details too aggressively, which is unsafe for production environments.

**Tasks**
- [ ] Remove or guard sensitive logs in [app/api/todos/route.ts](app/api/todos/route.ts)
- [ ] Remove or guard sensitive logs in [app/api/todos/bulk/route.ts](app/api/todos/bulk/route.ts)
- [ ] Keep only minimal sanitized error logging for operational troubleshooting
- [ ] Ensure endpoint behavior remains unchanged after cleanup

**Files to modify**
- [app/api/todos/route.ts](app/api/todos/route.ts)
- [app/api/todos/bulk/route.ts](app/api/todos/bulk/route.ts)

Start by reviewing the logging in app/api/todos/route.ts and app/api/todos/bulk/route.ts, focusing on request headers and token-related details. Remove or guard sensitive output while retaining minimal sanitized error logging, then exercise the todo endpoints to confirm their behavior remains unchanged.

Written by the indexing model from the issue text.