fix: add validation for unrecognized skills in input field

[shubh22-u]

Summary [required]

Related Issue [required]

Closes #

Type of Change [required]

• Bug fix — resolves a broken behaviour
• Feature — adds new functionality
• Data — adds new projects to data/projects.json
• Documentation — updates docs, README, or code comments only
• Style — CSS or visual changes only, no logic change
• Refactor — restructures code without changing behaviour
• Test — adds or updates tests

What Was Changed [required]

File	Change made
utils/recommender.py	Added clear_cache() function
tests/test_basic.py	Added test for cache invalidation

How to Test This PR [required]

1. Clone this branch: git checkout your-branch-name
2. Install dependencies: pip install -r requirements.txt
3. Run the app: python app.py
4. Open http://127.0.0.1:5000 and...
5. Run the tests: python tests/test_basic.py

Expected test output:

27 passed, 0 failed out of 27 tests

Test Results [required]

paste output here

Screenshots (if UI change)

Before	After
screenshot	screenshot

Self-Review Checklist [required]

• I have read CONTRIBUTING.md and followed all guidelines
• My branch name follows the convention: feat/, fix/, docs/, data/, style/, test/
• I have run python tests/test_basic.py and all 27 tests pass
• I have run flake8 . locally and there are no errors
• I have not introduced any print() or console.log() debug statements
• Every new function I wrote has a docstring
• I have not modified files outside the scope of the linked issue
• If I changed the UI, I tested it at 375px (mobile) and 1280px (desktop)
• If I added a project to the dataset, it has all required JSON fields

Notes for Reviewer

[vercel]

@shubh22-u is attempting to deploy a commit to the komalsony234-1530's projects Team on Vercel.

A member of the Team first needs to authorize it.