feat: migrate to DragonflyDB and clean up environment configuration

- Replace Redis with DragonflyDB for better performance and memory efficiency
- Remove redundant environment variables (POSTGRES_*, ENCRYPTION_KEY, OAUTH_SERVICE_URL)
- Consolidate database configuration to use single DB_* variables
- Use JWT_SECRET for both JWT tokens and encryption
- Remove PORT variable redundancy, use BACKEND_PORT consistently
- Clean up docker-compose configurations for dev/prod consistency
- Add DragonflyDB configuration with optimized memory usage
- Remove redis.conf as it's no longer needed
- Update health checks to use Redis-compatible CLI for DragonflyDB
- Add missing VITE_API_URL to production frontend
- Fix GitHub Actions to use correct go.sum path
- Clean up development directories and unused files

backend/Dockerfile

@@ -1,5 +1,5 @@
 # Build stage
-FROM golang:1.24-alpine AS builder
+FROM golang:1.25-alpine AS builder
 
 WORKDIR /app
 
@@ -27,6 +27,9 @@ WORKDIR /root/
 # Copy the binary from builder stage
 COPY --from=builder /app/main .
 
+# Copy migrations directory
+COPY --from=builder /app/migrations ./migrations
+
 # Create necessary directories
 RUN mkdir -p /app/uploads /data