feat: add large scale project conversion

[CybersharpX]

Summary

Adds end-to-end directory and project-level conversion to the transpiler framework.

Features

• Project Subsystem (transpiler.project):
  • ProjectScanner: Recursive discovery with .gitignore and glob filtering.
  • IncrementalCache: SHA-256 hash-based caching to skip unchanged files.
  • ProjectSymbolIndex: Cross-file symbol extraction for multi-file type inference.
  • manifest.py: Auto-generates Cargo.toml, package.json, go.mod, and __init__.py.
  • ProjectConverter: Multi-worker concurrent conversion (ThreadPoolExecutor) with error resilience.
  • FileResult & ConversionReport: Summary reporting and JSON export.
• Enhanced Type Inference: Pre-populates external function signatures for cross-file call type resolution.
• CLI Extensions: Supports directory inputs, -o/--output-dir, -j/--jobs, --incremental, --force, --copy-assets, --dry-run, --config, and --report.
• Configuration Support: Load settings from transpiler.json.

Testing

• 287/287 tests passing (pytest).
• Clean formatting and linting (black, ruff, mypy).