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, 8 insertions, 3 deletions

diff --git a/nix/module.nix b/nix/module.nix
index 4a6fc94..89d58de 100644
--- a/nix/module.nix
+++ b/nix/module.nix
@@ -127,9 +127,14 @@ let
       };
 
       logLevel = mkOption {
-        type = types.enum [ "trace" "debug" "info" "warn" "error" ];
+        type = types.str;
         default = "info";
-        description = "Logging level for RUST_LOG environment variable";
+        example = "debug";
+        description = ''
+          Logging level for application logging.
+          Can be a simple level (trace, debug, info, warn, error) or a filter expression.
+          Examples: "info", "debug", "ngit_grasp=debug,actix_web=info"
+        '';
       };
 
       syncMaxBackoffSecs = mkOption {
@@ -334,7 +339,7 @@ let
       NGIT_REPOSITORY_BLACKLIST = concatStringsSep "," cfg.repositoryBlacklist;
       NGIT_EVENT_BLACKLIST = concatStringsSep "," cfg.eventBlacklist;
       NGIT_MAX_CONNECTIONS = toString cfg.maxConnections;
-      RUST_LOG = cfg.logLevel;
+      NGIT_LOG_LEVEL = cfg.logLevel;
     } // optionalAttrs (cfg.relayName != null) {
       NGIT_RELAY_NAME = cfg.relayName;
     } // optionalAttrs (cfg.archiveReadOnly != null) {