Feat: Add anonymous post and reply functionality

[nysagarg04]

This PR implements the frontend UI for the anonymous post and reply feature. Users can now see two new buttons:
• Anonymous Post button, which opens a post dialogue.

•	Anonymous Reply button, which opens a reply dialogue.

Although the backend logic to handle anonymous posting isn’t fully functional yet (the post still shows the name of the user), the UI successfully persists after a page refresh, ensuring a smoother user experience.

Changes Introduced
• Added buttons for anonymous posting and replying.
• Implemented modal dialogues for submitting anonymous posts and replies.
• Ensured that the buttons remain visible after a page refresh (handled state persistence).

Challenges & Limitations
• Currently, posts do not appear as anonymous due to a complex backend issue.
• I sought assistance from TAs, but the issue requires further debugging.
• The next step is to resolve backend integration to ensure anonymity works correctly.

Next Steps
• Investigate and fix the backend issue preventing anonymous posts from appearing correctly.
• Test and validate the entire flow from UI to backend once the issue is resolved.

[ethan1696]

Looks great! Feel free to merge!

[coveralls]

Pull Request Test Coverage Report for Build 13572891965

Details

• 6 of 10 (60.0%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.002%) to 82.674%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/topics/posts.js	3	4	75.0%
src/controllers/composer.js	1	4	25.0%

Totals
Change from base Build 13571779325:	-0.002%
Covered Lines:	22355
Relevant Lines:	25619

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💛 - Coveralls