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, 5 insertions, 2 deletions

diff --git a/.env.example b/.env.example
index e152b89..01854f4 100644
--- a/.env.example
+++ b/.env.example
@@ -101,9 +101,12 @@
 # LOGGING
 # ============================================================================
 
-# Rust log level (not a ngit-grasp config, but useful for debugging)
+# Log level for application logging
+# CLI: --log-level <level>
+# Default: info
 # Options: error, warn, info, debug, trace
-# RUST_LOG=info
+# Can also use filter expressions: ngit_grasp=debug,actix_web=info
+# NGIT_LOG_LEVEL=info
 
 # ============================================================================
 # PROACTIVE SYNC (GRASP-02)