fix: clean up Phase 1/2 commit issues

- Remove duplicate HTTP_STATUS/NETWORK exports in constants.js
- Remove unused responseHelpers import from server.js
- Remove backup file and doc artifacts from tracking
- Update .gitignore to prevent re-adding bloat files

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

dashcaddy-api/constants.js

@@ -183,8 +183,4 @@ module.exports = {
   buildMediaAuth,
   HTTP_STATUS,
   NETWORK,
-  HTTP_STATUS,
-  NETWORK,
 };
-
-