feat: add dynamic fallback message for empty area of interest

[HariniGS-1207]

Summary
This PR adds a dynamic fallback message for empty areas of interest. When a user selects a technical interest category that does not currently have any project recommendations available in the repository, the application will now return an empty projects array along with a user-friendly message rather than breaking or throwing a generic error.
Related Issue [required]

Closes #297 Type of Change

• Feature — adds new functionality.
• Style — CSS or visual changes only, no logic change.

How to Test This PR

• Clone this branch: git checkout fix/add-more-intrest-section.
• Install dependencies: pip install -r requirements.txt.
• Run the app: python app.py
• Open http://127.0.0.1:5000/ and select one of the newly added interest dropdown areas (e.g., "Machine Learning/AI").
• Verify that the UI gracefully hides the grid and displays: "No projects are currently available for this interest. Please check back later or try a different area."

Run the tests: python tests/test_basic.py

**Test Results **
28 passed, 0 failed out of 28 tests

Self-Review Checklist

• 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 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).

ScreenShots

Notes for Reviewer
None.

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[HariniGS-1207]

Hi @komalharshita ,

I have completed the PR template, linked the issue, and verified that all 28 tests pass successfully locally.
Could a you please approve the workflows to run and review my changes when you have a moment? Thank you!

[komalharshita]

@HariniGS-1207 ensure that all checks pass before merging

[HariniGS-1207]

Hi @komalharshita, the Vercel check is currently waiting for authorization from a maintainer to run. Could you please approve/authorize the workflow so the check can pass? All local tests are passing successfully!

[komalharshita]

@HariniGS-1207 resolve the merge conflicts