Fix/pylint cleanup (#8)

* Fix pylint warnings across all 24 Python files in web_server

- Add module, class, and function docstrings (C0114, C0115, C0116)
- Fix import ordering: stdlib before third-party before local (C0411)
- Replace wildcard imports with explicit named imports (W0401)
- Remove trailing whitespace and add missing final newlines (C0303, C0304)
- Replace dict() with dict literals (R1735)
- Remove unused imports and variables (W0611, W0612)
- Narrow broad Exception catches to specific exceptions (W0718)
- Replace f-string logging with lazy % formatting (W1203)
- Fix variable naming: UPPER_CASE for constants, snake_case for locals (C0103)
- Add pylint disable comments for necessary global statements (W0603)
- Fix no-else-return, simplifiable-if-expression, singleton-comparison
- Fix bad indentation in stripe.py (W0311)
- Add encoding="utf-8" to open() calls (W1514)
- Add check=True to subprocess.run() calls (W1510)
- Register Celery task modules via conf.include

* Update `package-lock.json` add peer dependencies

web_server/blueprints/middleware.py

@@ -1,7 +1,10 @@
-from flask import redirect, g, session
-from functools import wraps
+"""Authentication middleware and error handler registration."""
+
 import logging
+from functools import wraps
 from os import getenv
+
+from flask import redirect, g, session
 from dotenv import load_dotenv
 from database.database import Database
 
@@ -57,5 +60,5 @@ def register_error_handlers(app):
     for code, message in error_responses.items():
         @app.errorhandler(code)
         def handle_error(error, message=message, code=code):
-            logging.error(f"Error {code}: {str(error)}")
-            return {"error": message}, code
+            logging.error("Error %d: %s", code, str(error))
+            return {"error": message}, code