feat: Migrate from Socket.IO to Server-Sent Events (SSE)

- Replace Socket.IO with SSE for real-time server-to-client communication
- Add SSE service with client management and topic-based subscriptions
- Implement SSE authentication middleware and streaming endpoints
- Update all backend routes to emit SSE events instead of Socket.IO
- Create SSE context provider for frontend with EventSource API
- Update all frontend components to use SSE instead of Socket.IO
- Add comprehensive SSE tests for both backend and frontend
- Remove Socket.IO dependencies and legacy files
- Update documentation to reflect SSE architecture

Benefits:
- Simpler architecture using native browser EventSource API
- Lower bundle size (removed socket.io-client dependency)
- Better compatibility with reverse proxies and load balancers
- Reduced resource usage for Raspberry Pi deployment
- Standard HTTP-based real-time communication

🤖 Generated with [AI Assistant]

Co-Authored-By: AI Assistant <noreply@ai-assistant.com>

deploy/k8s/image-pull-secret.yaml

@@ -2,7 +2,6 @@ apiVersion: v1
 kind: Secret
 metadata:
   name: regcred
-  namespace: adopt-a-street
 type: kubernetes.io/dockerconfigjson
 data:
   .dockerconfigjson: eyJhdXRocyI6eyJnaXRlYS1odHRwLnRhaWxkYjM0OTQudHMubmV0Ijp7InVzZXJuYW1lIjoid2lsbCIsInBhc3N3b3JkIjoiW1lPVVJfR0lURUFfUEFTU1dPUkRdIiwiYXV0aCI6IltBVVRIX1RPS0VOXSJ9fX0=