chore: remove development files not needed for PR

- Remove CLAUDE.md (local development guide)
- Remove gemini-plan.md (implementation planning doc)
- Simplify .gitignore to only add .env (generic ignore)

Author: cuipengfei

.gitignore

@@ -12,7 +12,6 @@ node_modules/
 
 # build output
 dist/
-logs/gemini-debug.log
-logs/gemini-translation.log
+
+# environment variables
 .env
-logs/gemini-errors.log