feat: security hardening — SSRF guard, template sandbox timeout, webhook log prune, auth & backup polish

- Add outbound URL validation (SSRF) for webhook/Discord/Slack/ntfy/Matrix dispatch
- Template renderer: input/output caps and thread-based render timeout
- Webhook log filter: strip Authorization/signature/token-like headers; atomic prune
- Auth/JWT/backup/config tightening; misc frontend UX fixes

packages/server/src/notify_bridge_server/services/dispatch_helpers.py

@@ -249,6 +249,22 @@ async def load_link_data(
             event_key = s.slot_name.removeprefix("message_") if s.slot_name.startswith("message_") else s.slot_name
             slots_by_config.setdefault(s.config_id, {}).setdefault(event_key, {})[s.locale] = s.template
 
+    # Pre-resolve broadcast children in one query to avoid N+1 per-child fetches
+    broadcast_child_ids: set[int] = set()
+    for tt in active_links:
+        target = target_map.get(tt.target_id)
+        if target and target.type == "broadcast":
+            disabled_ids = set(target.config.get("disabled_child_ids", []))
+            for cid in target.config.get("child_target_ids", []):
+                if cid not in disabled_ids:
+                    broadcast_child_ids.add(cid)
+    child_target_map: dict[int, NotificationTarget] = {}
+    if broadcast_child_ids:
+        child_rows = await session.exec(
+            select(NotificationTarget).where(NotificationTarget.id.in_(broadcast_child_ids))
+        )
+        child_target_map = {t.id: t for t in child_rows.all()}
+
     link_data: list[dict[str, Any]] = []
     for tt in active_links:
         target = target_map.get(tt.target_id)
@@ -262,14 +278,13 @@ async def load_link_data(
         template_config = tmpl_map.get(tmpl_id) if tmpl_id else None
         template_slots = slots_by_config.get(template_config.id) if template_config else None
 
-        # Broadcast target: expand into child targets
+        # Broadcast target: expand into child targets (pre-loaded above)
         if target.type == "broadcast":
-            child_ids = target.config.get("child_target_ids", [])
             disabled_ids = set(target.config.get("disabled_child_ids", []))
-            for child_id in child_ids:
+            for child_id in target.config.get("child_target_ids", []):
                 if child_id in disabled_ids:
                     continue
-                child_target = await session.get(NotificationTarget, child_id)
+                child_target = child_target_map.get(child_id)
                 if not child_target or child_target.type == "broadcast":
                     continue
                 resolved = await _resolve_target(session, child_target)