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, 25 insertions, 12 deletions

diff --git a/docs/reference/configuration.md b/docs/reference/configuration.md
index b24b498..b09b20f 100644
--- a/docs/reference/configuration.md
+++ b/docs/reference/configuration.md
@@ -1041,10 +1041,10 @@ Per-connection limits (built-in to relay-builder, not configurable):
 
 ### Logging Configuration
 
-#### `RUST_LOG`
+#### `NGIT_LOG_LEVEL`
 
-**Description:** Logging level and filters (standard Rust environment variable)  
-**Type:** String (log level or filter)  
+**Description:** Logging level and filters for application logging  
+**Type:** String (log level or filter expression)  
 **Default:** `info`  
 **Required:** No
 
@@ -1052,17 +1052,17 @@ Per-connection limits (built-in to relay-builder, not configurable):
 
 ```bash
 # Simple levels
-RUST_LOG=error    # Errors only
-RUST_LOG=warn     # Warnings and errors
-RUST_LOG=info     # Info, warnings, errors
-RUST_LOG=debug    # Debug and above
-RUST_LOG=trace    # Everything
+NGIT_LOG_LEVEL=error    # Errors only
+NGIT_LOG_LEVEL=warn     # Warnings and errors
+NGIT_LOG_LEVEL=info     # Info, warnings, errors (default)
+NGIT_LOG_LEVEL=debug    # Debug and above
+NGIT_LOG_LEVEL=trace    # Everything (very verbose)
 
-# Module-specific
-RUST_LOG=ngit_grasp=debug,actix_web=info
+# Module-specific filtering
+NGIT_LOG_LEVEL=ngit_grasp=debug,actix_web=info
 
 # Complex filters
-RUST_LOG=debug,hyper=info,tokio=warn
+NGIT_LOG_LEVEL=debug,hyper=info,tokio=warn
 ```
 
 **Log levels (most to least verbose):**
@@ -1073,12 +1073,25 @@ RUST_LOG=debug,hyper=info,tokio=warn
 4. `warn` - Warnings about potential issues
 5. `error` - Errors only
 
+**CLI flag:**
+
+```bash
+ngit-grasp --log-level trace
+```
+
 **Production recommendation:**
 
 ```bash
-RUST_LOG=info,ngit_grasp=debug
+NGIT_LOG_LEVEL=info
 ```
 
+**Notes:**
+
+- Uses Rust's `tracing` crate filter syntax
+- Supports module-level filtering (e.g., `ngit_grasp=debug,hyper=info`)
+- `trace` level can significantly impact performance
+- For production, `info` or `warn` is recommended
+
 ---
 
 ### Security Configuration (Planned)