fix: issues with pull_request:null no longer classified as PRs

Gitea API returns 'pull_request': null for regular issues.
Old filter 'pull_request' in issue matched the key even when null,
sending ALL issues to the PRs section instead of the Kanban columns.
Fixed: i.get('pull_request') — null is falsy, real PR dict is truthy.

Also: labels/milestones dropdowns empty = repo has none configured in Gitea.

app/routers/board.py

@@ -65,8 +65,8 @@ async def board(
         if assignee:
             issues = [i for i in issues if i.get("assignee", {}).get("login") == assignee]
 
-        prs = [i for i in issues if "pull_request" in i]
-        issues_only = [i for i in issues if "pull_request" not in i]
+        prs = [i for i in issues if i.get("pull_request")]
+        issues_only = [i for i in issues if not i.get("pull_request")]
 
         board_info = _ensure_board(owner, repo)
         columns = board_info["columns"]