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/data/batch.rs

@@ -54,10 +54,7 @@ pub async fn batch_upsert_courses(courses: &[Course], db_pool: &PgPool) -> Resul
 
     let subjects: Vec<&str> = courses.iter().map(|c| c.subject.as_str()).collect();
 
-    let course_numbers: Vec<&str> = courses
-        .iter()
-        .map(|c| c.course_number.as_str())
-        .collect();
+    let course_numbers: Vec<&str> = courses.iter().map(|c| c.course_number.as_str()).collect();
 
     let titles: Vec<&str> = courses.iter().map(|c| c.course_title.as_str()).collect();