Merge relay.ngit.dev migration: bug fixes and migration tooling

This merge includes critical bug fixes and comprehensive migration tooling
developed during the relay.ngit.dev migration effort.

Bug Fixes:
- Fix git protocol error handling to return HTTP 200 with ERR pkt-line
- Fix naughty list false positives and DNS failure identification
- Fix database query filters in load_existing_events (remove .since())
- Fix OID fetch tracking to distinguish 0 OIDs from successful fetches
- Fix purgatory event source tracking for filtered expiry logging
- Implement OID retry logic for 'not our ref' errors

Migration Tools & Documentation:
- Complete 5-phase migration analysis pipeline with orchestration script
- Phase 1: Event fetching from source relay
- Phase 2: Git sync verification
- Phase 3: Categorization and relay comparison
- Phase 4: Log extraction (parse failures, purgatory expiry)
- Phase 5: Action classification for migration decisions
- Comprehensive migration guide with lessons learned
- Troubleshooting guide for permission and corruption issues

Configuration:
- Add NGIT_LOG_LEVEL configuration option
- Update git throttle limits to 60/minute
- Improve logging throughout for better observability

1 files changed, 0 insertions, 12 deletions

diff --git a/docs/how-to/README.md b/docs/how-to/README.md
index ba58c08..087ae53 100644
--- a/docs/how-to/README.md
+++ b/docs/how-to/README.md
@@ -110,18 +110,6 @@ How-to guides are **recipes** that show you how to solve specific problems or ac
 
 ---
 
-### Migrate from ngit-relay
-**Status:** 🔜 Planned
-
-**Problem:** Switch from reference implementation  
-**You'll learn:**
-- Export data from ngit-relay
-- Import to ngit-grasp
-- Update repository URLs
-- Verify migration
-
----
-
 ## How to Use How-To Guides
 
 1. **Find your problem** - Browse or search for what you need