feat: broadcast notification target + UX improvements

Add broadcast target type that fans out notifications to multiple
child targets. Dispatch expands broadcast into children in
load_link_data() — dispatcher stays unaware. Children can be
toggled on/off via disabled_child_ids in config.

Also: dashboard provider card smaller font for names, scroll-to-form
on target edit, broadcast nav tab with counter, flag_modified fix
for JSON column updates, CLAUDE.md nav tree docs.

scripts/restart-backend.sh

@@ -15,7 +15,7 @@ fi
 # Start backend
 NOTIFY_BRIDGE_DATA_DIR=./test-data \
 NOTIFY_BRIDGE_SECRET_KEY=test-secret-key-minimum-32chars \
-PYTHON=$(command -v python3 2>/dev/null || command -v python 2>/dev/null || command -v py 2>/dev/null)
+PYTHON=$(command -v python3 2>/dev/null || command -v python 2>/dev/null || echo "py -3.13")
 nohup "$PYTHON" -m uvicorn notify_bridge_server.main:app \
   --host 0.0.0.0 --port 8420 > /dev/null 2>&1 &