fix: Prevent bot self-trigger infinite loops in all workflows

CRITICAL FIX: Bot was triggering itself causing 10+ duplicate runs

Problem:
- When bot posts comments containing @codebot (e.g., help responses, PR reviews)
- Workflows trigger on those bot comments
- Bot responds again with @codebot mention
- Infinite loop → 10+ duplicate workflow runs → excessive API costs

Solution:
- Added github.event.comment.user.login != 'Bartender' to all workflow conditions
- Prevents bot from reacting to its own comments
- Bot username 'Bartender' is now hardcoded in workflows

Changes:
- .gitea/workflows/ai-comment-reply.yml: Added bot username check
- .gitea/workflows/ai-chat.yml: Added bot username check
- .gitea/workflows/ai-issue-triage.yml: Added bot username check
- CLAUDE.md: Documented bot self-trigger prevention and username update instructions
- README.md: Added Step 3 to bot customization with critical warning

Impact:
- Eliminates infinite loop scenarios
- Prevents excessive API costs from duplicate runs
- Workflows only trigger on human user comments

Note: If bot username changes from 'Bartender', all three workflow files must be updated.

.gitea/workflows/ai-comment-reply.yml

@@ -17,7 +17,9 @@ jobs:
         runs-on: ubuntu-latest
         # Only run for specific commands (not free-form chat or triage)
         # This prevents duplicate runs with ai-chat.yml and ai-issue-triage.yml
+        # CRITICAL: Ignore bot's own comments to prevent infinite loops (bot username: Bartender)
         if: |
+            github.event.comment.user.login != 'Bartender' &&
             (contains(github.event.comment.body, '@codebot help') ||
              contains(github.event.comment.body, '@codebot explain') ||
              contains(github.event.comment.body, '@codebot suggest') ||