feat: add strict mypy type-checking for app/utils/ module

- Add [[tool.mypy.overrides]] section for app/utils/** with disallow_untyped_defs=true
- Add type annotations to all functions in app/utils/ (12 files)
- Fix type annotations in app/config.py and app/database.py (imported by utils)
- All 85 source files now pass mypy type checking

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

app/utils/file_operations.py

@@ -1,7 +1,8 @@
 import hashlib
+from pathlib import Path
 
 
-def hash_file(filepath, chunk_size=65536):
+def hash_file(filepath: str | Path, chunk_size: int = 65536) -> str:
     """
     Returns the SHA-256 hash of the file at 'filepath'.
     Reads the file in chunks to handle large files efficiently.