feat: modernize build tooling and add CI/CD workflow

Switch to Bun for 2-5x faster frontend builds, implement cargo-chef for
reliable Rust dependency caching, and add Biome for fast code
formatting.

Build system improvements:
- Replace pnpm with Bun for frontend package management
- Add cargo-chef to Dockerfile for better Rust build layer caching
- Update all commands to use bun instead of pnpm

Developer experience:
- Add comprehensive Justfile commands (format, format-check, db)
- Implement automated PostgreSQL Docker setup with random port
allocation
- Add stricter checks (--deny warnings on clippy, --all-features flag)

Code quality:
- Add Biome formatter for 10-100x faster TypeScript/JavaScript
formatting
- Add GitHub Actions CI/CD workflow for automated checks
- Update .dockerignore with comprehensive exclusions
- Format all code with cargo fmt (Rust) and Biome (TypeScript)

All changes maintain backward compatibility and can be tested
incrementally.

src/app.rs

@@ -124,7 +124,7 @@ impl App {
     /// Setup bot service if enabled
     pub async fn setup_bot_service(&mut self) -> Result<(), anyhow::Error> {
         use std::sync::Arc;
-        use tokio::sync::{broadcast, Mutex};
+        use tokio::sync::{Mutex, broadcast};
 
         // Create shutdown channel for status update task
         let (status_shutdown_tx, status_shutdown_rx) = broadcast::channel(1);