v2.5.1: adaptive retry for 429/502/503, socket reuse, BGP retry

- Exponential backoff retry (2s/4s/8s) for rate limits and transient errors
- BGP routes retry before failing over to next route
- Socket SO_REUSEADDR prevents 'Address already in use' crashes
- Connection reset/broken pipe also retried
- BGP route count shown at proxy startup

CHANGELOG.md

@@ -1,5 +1,15 @@
 # Changelog
 
+## v2.5.1 (2026-05-20)
+
+- **Adaptive retry for transient errors** (429/502/503)
+  - Exponential backoff: 2s → 4s → 8s, up to 3 retries
+  - Works for both single-provider and BGP mode
+  - BGP routes retry before failing over to next route
+  - Connection errors (reset/broken pipe) also retried
+- **Proxy socket reuse** — no more `Address already in use` crashes on restart
+- **BGP startup log** shows route count and names
+
 ## v2.5.0 (2026-05-20)
 
 - **AI BGP — Multi-provider routing with automatic failover**