refactor(imessage): address PR review comments

- Add get_param_u32/get_param_str helpers to reduce param parsing boilerplate
- Add enrich_* methods for consistent contact enrichment
- Add time constants (SECONDS_PER_DAY, NANOS_PER_SECOND) for self-documenting code
- Extract RECENT_MESSAGES SQL to queries.rs for consistency
- Fix potential panic in days_ago_from_cocoa (handle clock adjustments gracefully)
- Refactor bundle handler to use shared enrichment methods
- Optimize analytics from 20ms to 5.7ms via combined SQL query

Addresses review feedback from Gemini Code Assist and GitHub Copilot.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: wolfiesch