build(deps): migrate to hatchling, enforce strict typing, and optimize config

[JacksonFergusonDev]

Summary

This PR overhauls the build system and developer tooling to improve reliability and code quality. It migrates the build backend to Hatchling, enforces strict Mypy type checking, and prevents repository bloat via .gitattributes.

Key Changes

🛠 Build & Configuration

• Build System: Migrated from legacy setuptools (implicit) to Hatchling.
• Git Attributes: Added .gitattributes to treat PDFs (*.pdf) and uv.lock as binary files, preventing corrupted text diffs and merge conflicts.
• Dependencies: Synced requirements.txt with uv.lock to ensure Streamlit Cloud deployments match the local dev environment.

🛡 Code Quality & Linting

• Mypy (Strict Mode): Enabled check_untyped_defs = true globally.
  • Note: Added overrides to relax strictness for tests/* and app.py (UI layer).
  • Added tests/__init__.py to resolve namespace package discovery issues.
• Ruff Rules: Enabled additional rule sets:
  • T20 (No print statements in core lib).
  • PT (Pytest style best practices).
  • C4 (List/Set comprehension optimizations).

🧹 Refactoring

• Type Safety: Updated src/bom_lib and src/exporters.py to fix type narrowing errors found by the new Mypy rules.
• Performance: Refactored app.py and presets.py to remove redundant list() calls inside sorted() (Ruff C414/C401).
• Tools: Exempted tools/ scripts from the "no print" rule to allow CLI output.

Testing

• Running uv run mypy . now passes with zero errors.
• Running uv run ruff check . passes with zero errors.
• tests/ suite passes successfully.