feat: implement image proxy for YouTube CDN images with caching to prevent rate limits

memory-bank/activeContext.md

@@ -7,6 +7,7 @@
 - **Rich message parsing**: Full support for superchats, memberships, badges (moderator, member, verified)
 - **Timezone-aware timestamps**: All message timestamps display in user's local timezone with proper browser detection
 - **Visual selection feedback**: Previously selected messages show dimmed state for better user experience
+- **Image proxy implemented**: Backend proxies all YouTube CDN images with caching to prevent 429 rate limit errors
 
 ## Recent Decisions
 - Fixed CORS issues by setting headers on raw response object after `reply.hijack()` for SSE endpoint
@@ -24,14 +25,16 @@
 - **Timezone Support**: Implemented browser timezone detection and proper timestamp formatting across dashboard and overlay using `Intl.DateTimeFormat` with GMT+3 fallback.
 - **Visual Selection States**: Added three-tier visual feedback system - active (selected), normal, and previously-selected (dimmed) states for better user experience.
 - **UI Polish**: Fixed pulse animations on initial load, hidden N/A messages, and improved overlay timestamp display.
+- **Image Proxy**: Added `/proxy/image` endpoint in backend with in-memory caching (24hr TTL, max 1000 images) to prevent YouTube CDN 429 rate limit errors. All avatars, badges, and emojis now route through proxy with stale-on-error fallback.
 
 ## Immediate Next Steps
 1. Test with live YouTube stream to verify badge parsing and superchat detection
 2. Add search/filter functionality for chat messages
 3. Implement error recovery and reconnection logic for stream interruptions
 4. Add keyboard shortcuts for quick message selection
+5. Consider persistent cache for images (SQLite or file-based) for better reliability
 
 ## Open Questions
 - Whether to add message search/filtering UI controls
-- How to handle rate limiting and backoff strategies for long streams
 - Whether to persist Innertube visitor data between runs
+- Should image cache be persistent across restarts?

memory-bank/progress.md

@@ -34,6 +34,7 @@
 - [ ] Add theme controls and customization options.
 
 ## Phase 4 – Reliability & Polish
+- [x] Implement image proxy with caching to prevent YouTube CDN 429 errors.
 - [ ] Expand logging/metrics for long-stream observability.
 - [ ] Write tests (unit/integration) and contributor documentation.
 
@@ -47,4 +48,5 @@
 - **✅ Timestamp Resolution Fixed**: Critical bug resolved - timestamps now display correct current time instead of 1970 epoch
 - **✅ Timezone Support**: All timestamps display in user's local timezone with browser detection and GMT+3 fallback
 - **✅ Visual Selection States**: Three-tier feedback system (active/normal/previously-selected) for better UX
+- **✅ Image Proxy Implemented**: Backend now proxies all YouTube CDN images (avatars, badges, emojis) with 24hr in-memory cache to prevent 429 rate limit errors
 - **Next**: Add search/filter, error recovery, and polish UX details

memory-bank/systemPatterns.md

@@ -18,3 +18,4 @@
 - **Timezone Context Pattern**: React context provider (`TimezoneContext`) manages browser timezone detection and shares across components for consistent timestamp formatting.
 - **Selection State Management**: Three-tier visual state system (active/selected, normal, previously-selected) with CSS class composition for clear user feedback.
 - **Timestamp Resolution**: Backend uses `timestamp_usec` (microseconds) from YouTube data, converts to milliseconds, and frontend formats in user's local timezone.
+- **Image Proxy Pattern**: Backend `/proxy/image` endpoint caches YouTube CDN images (avatars, badges, emojis) with MD5-hashed keys, 24hr TTL, and 1000-image LRU eviction. Returns stale cache on 429 errors or network failures. Frontend `proxyImageUrl()` helper transparently rewrites YouTube CDN URLs to use proxy.