fix: add TTL cleanup for pendingReplies memory leak

[kumudasrip]

Description of Changes

Implemented a TTL-based cleanup mechanism for the pendingReplies map to prevent unbounded memory growth in long-running deployments.

Changes made:

• Added lastActivityAtMs tracking for each pending reply entry.

• Implemented automatic cleanup of stale inactive entries.

• Added configurable environment variables:

  • CHAT_BUDDY_PENDING_REPLY_TTL_HOURS
  • CHAT_BUDDY_PENDING_REPLY_CLEANUP_INTERVAL_MS

• Added interval lifecycle management to avoid unnecessary timers.

• Ensured cleanup timers and pending timeouts are gracefully terminated during bot shutdown.

• Added validation and clamping for TTL and cleanup interval values.

• Updated:

  • .env.example
  • README.md
  • CONTRIBUTING.md
  • CHANGELOG.md
  • architecture documentation
  • docker-compose configuration

This prevents inactive users from remaining indefinitely in memory and stabilizes memory usage for long-running bot instances.

Related Issue Number

Closes #45

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• Documentation update
• Refactor or other maintenance

How Was This Tested?

Manual Testing

1. Started the bot using:

   npm run start

2. Verified:

   • inactive entries were automatically removed after TTL expiry
   • cleanup interval executed correctly
   • active conversations were not removed
   • cleanup timers stopped when map became empty
   • shutdown cleared all intervals and timeouts properly

3. Tested different environment variable values:

   CHAT_BUDDY_PENDING_REPLY_TTL_HOURS=1
   CHAT_BUDDY_PENDING_REPLY_CLEANUP_INTERVAL_MS=300000

Build Verification

npm run build

Additional Validation

• Verified no regression in debounce behavior.
• Confirmed memory usage remains stable during long-running tests with multiple simulated users.

Checklist

• The code builds without errors (npm run build).
• Existing tests pass (npm test).
• Documentation has been updated to reflect these changes if needed.

[kumudasrip]

Hello @snackoverflowasad , This PR fixes issue #45
Please do review and merge the PR under GSSoC 2026 whenever possible.. Thank you!

[snackoverflowasad]

Hey @kumudasrip please check for ci builds test

[kumudasrip]

I have updated the changes for ci build tests failure
@snackoverflowasad @shouri123 please do review it once again whenever possible, thank you!

[shouri123]

I have updated the changes for ci build tests failure
@snackoverflowasad @shouri123 please do review it once again whenever possible, thank you!

Sime checks are not running

[shouri123]

@kumudasrip please check again the prs it not running the checks are not running

[kumudasrip]

@kumudasrip please check again the prs it not running the checks are not running

Resolving them, I will open a new PR