Optimized Docker Image with Multi-Stage Build

### Summary This PR significantly reduces the Docker image size from **2.7GB to ~250MB** (over 90% reduction) by implementing a multi-stage build approach and removing unnecessary build dependencies from the final image. ### Changes Made #### 1. **Multi-Stage Build Architecture** - **Builder Stage**: Contains all build tools (Go, Node.js, Task, Goose, SQLC, golangci-lint) - **Runtime Stage**: Uses `debian:trixie-slim` with only essential runtime dependencies #### 2. **Dependency Optimization** **Removed from final image:** - Go compiler and toolchain - Node.js and npm - Task runner (except Goose for migrations) - SQLC and golangci-lint - Wget, unzip, git, and other build tools **Retained in final image:** - PostgreSQL clients (13-18) for backup operations - Goose binary for database migrations - Application binaries (`app` and `change-password`) - Static files #### 3. **Security Improvements** - Created non-root user `pgbackweb` for application execution - Removed build tools that could be exploited - Minimal attack surface with only required packages #### 4. **Migration Handling** - Migration files are copied to the final image for runtime use #### 5. **Build Process** - All compilation happens in the builder stage - Only compiled binaries and runtime dependencies are copied to final image ### Benefits - **10x smaller image** (2.7GB → ~250MB) - **Faster deployments** and reduced storage costs - **Improved security** with fewer packages and non-root user - **Same functionality** with optimized resource usage