feat(worker): Listen for proxy_added notifications

- Workers now use PostgreSQL LISTEN/NOTIFY to wake up immediately when proxies are added
- Added trigger on proxies table to NOTIFY 'proxy_added' when active proxy inserted/updated
- Falls back to 30s polling if LISTEN fails

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/migrations/082_proxy_notification_trigger.sql

@@ -0,0 +1,27 @@
+-- Migration: 082_proxy_notification_trigger
+-- Date: 2024-12-11
+-- Description: Add PostgreSQL NOTIFY trigger to alert workers when proxies are added
+
+-- Create function to notify workers when active proxy is added/activated
+CREATE OR REPLACE FUNCTION notify_proxy_added()
+RETURNS TRIGGER AS $$
+BEGIN
+  -- Only notify if proxy is active
+  IF NEW.active = true THEN
+    PERFORM pg_notify('proxy_added', NEW.id::text);
+  END IF;
+  RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+-- Drop existing trigger if any
+DROP TRIGGER IF EXISTS proxy_added_trigger ON proxies;
+
+-- Create trigger on insert and update of active column
+CREATE TRIGGER proxy_added_trigger
+AFTER INSERT OR UPDATE OF active ON proxies
+FOR EACH ROW
+EXECUTE FUNCTION notify_proxy_added();
+
+COMMENT ON FUNCTION notify_proxy_added() IS
+'Sends PostgreSQL NOTIFY to proxy_added channel when an active proxy is added or activated. Workers LISTEN on this channel to wake up immediately.';