Why is this Change Important & Necessary?

Related to #11999
The current chatroom anonymous name system uses a deterministic hash-based approach (md5(user_id + chatroom_id + host_id + session_time)), which has several security and UX issues:

• Reverse-engineerable: Names can be predicted/reconstructed from known values
• Deterministic: Same user always gets the same name pattern
• No persistence: Names don't persist across chatroom sessions properly
• Limited namespace: Hash collisions possible with many users
• This PR replaces it with a secure, database-backed random name generation system that prevents reverse-engineering, ensures uniqueness, and persists names across sessions.

What is the New Behavior?

• Random human-readable names: "SwiftPanda427", "BraveDolphin892"
• 1.44M unique combinations (40 adjectives × 40 animals × 900 numbers)
• Names stored in database and persist across sessions
• Users can regenerate their name via new UI button
• Database constraints prevent duplicate names in same chatroom

Chatroom Header (Anonymous Mode):
[Chatroom Name] [Your Name: SwiftPanda427] [🔄 Regenerate Name] [Leave]

What steps should a reviewer take to reproduce or test the bug or new feature?

1. Run Database Migration

cd migration
sudo python3 run_migrator.py -e course migrate

Verify table created:

psql submitty_s24_sample
\dt chatroom_anonymous_names
\d chatroom_anonymous_names

2. Test Anonymous Name Generation

• Login as a student
• Navigate to a chatroom that allows anonymous mode
• Enable anonymous mode
• Expected: See a random name like "SwiftPanda427" (not a hash)
• Send a message
• Expected: Message shows anonymous name

3. Test Name Persistence

• Leave the chatroom
• Re-enter the chatroom (anonymous mode)
• Expected: Same anonymous name appears ("SwiftPanda427")
• Verify in database:

SELECT * FROM chatroom_anonymous_names;

Automated Testing & Documentation

1. Unit Tests
   ✅ Name generation logic tested (40×40×900 combinations)
   ✅ Collision detection verified
   ✅ Database uniqueness constraints enforced
   ⚠️ TODO: Add integration tests for UI button interaction Create issue

2. End-to-End Tests
   ⚠️ TODO: Add Cypress/Selenium tests for chatroom regenerate flow [Create issue]

Other information

1. Breaking Changes

• ❌ No breaking changes
• Old chatrooms continue to work (migration is additive)
• Existing anonymous sessions will get new names on first re-entry

2. Database Migration

• ✅ Includes migration: migration/migrator/migrations/course/20260226143000_chatroom_anonymous_names.py
• Creates new table: chatroom_anonymous_names
• No data loss - migration is purely additive
• Indexes added for query performance
• Foreign key constraints with CASCADE delete

3. Rollback Plan
   If issues arise:

-- Remove table (data loss, but chatrooms still functional)
DROP TABLE chatroom_anonymous_names;

-- Revert code changes via git
git revert <commit-hash>