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.

.dockerignore

@@ -13,6 +13,16 @@ go/
 # Development configuration
 bacon.toml
 .env
+.env.*
+!.env.example
+
+# CI/CD
+.github/
+.git/
+
+# Development tools
+Justfile
+rust-toolchain.toml
 
 # Frontend build artifacts and cache
 web/node_modules/
@@ -20,4 +30,22 @@ web/dist/
 web/.vite/
 web/.tanstack/
 web/.vscode/
+
+# IDE and editor files
 .vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# OS files
+.DS_Store
+Thumbs.db
+
+# Test coverage
+coverage/
+*.profdata
+*.profraw
+
+# SQLx offline mode (include this in builds)
+!.sqlx/