fix: add .local_version to GitignoreTemplate

Fixes #460 - .local_version was added for version tracking but not
included in the gitignore template, causing it to show as untracked.

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

cmd/bd/doctor/gitignore.go

@@ -20,6 +20,9 @@ daemon.log
 daemon.pid
 bd.sock
 
+# Local version tracking (prevents upgrade notification spam after git ops)
+.local_version
+
 # Legacy database files
 db.sqlite
 bd.db