sanitise keywords query param to prevent IndexError crash and abuse (#140)

[ahmedk20]

Description

Added a _validate_keyword() helper in routes/NewsRoutes.py that validates
the ?keywords= query parameter before it reaches the controller or database.
Both /<llm_name>/news_keywords and /raw/news_keywords now use it.

Related Issue

Fixes #140

Motivation and Context

The keywords endpoint passed user input directly to Pinecone with zero
validation, causing three problems:

1. Crash — IndexError on missing param

GET /mistralai/news_keywords        ← no ?keywords= provided
→ user_keywords = []
→ user_keywords[0]                  ← IndexError → unhandled 500

2. Empty input passes through

GET /mistralai/news_keywords?keywords=   ← only whitespace
→ blank string gets embedded and sent to Pinecone
→ wastes API quota and returns garbage results

3. No length limit

GET /mistralai/news_keywords?keywords=<10,000 chars>
→ goes straight into HuggingFace embedding call
→ risks hitting token limits and slowing the server

How Has This Been Tested?

Added 4 unit tests in tests/unitTest.py covering each validation case:

Test	Input	Expected
test_keywords_missing_param	no ?keywords=	400
test_keywords_empty_string	?keywords=	400
test_keywords_too_long	keyword > 200 chars	400
test_raw_keywords_missing_param	/raw/news_keywords no param	400

Results:

tests/unitTest.py::FlaskAppTestCase::test_keywords_missing_param     PASSED
tests/unitTest.py::FlaskAppTestCase::test_keywords_empty_string      PASSED
tests/unitTest.py::FlaskAppTestCase::test_keywords_too_long          PASSED
tests/unitTest.py::FlaskAppTestCase::test_raw_keywords_missing_param PASSED

4 passed in 3.29s

Testing environment: Python 3.14.2, Flask test client.
Validation runs entirely before any external call is made, so dummy
env vars for Pinecone/HuggingFace are sufficient to run these tests.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[arjunKalare]

Hi @ahmedk20, this was an issue that I raised and it is therefore up to our mentor @hardik1408 to determine who gets assigned the issue. You opening a PR on this issue without assignment is directly going against the protocol that is outlined in the contributions document.