Add default-server ntfy auth (fix 403 on protected topics)

The "send test" action, admin alerts and feeds without their own
credentials now use configurable default-server token / basic auth,
so publishing works against ntfy servers with access control enabled.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/delivery.py

@@ -95,6 +95,12 @@ async def dispatch(feed: Feed, settings: Settings, msg: Message) -> DispatchResu
     server = feed.ntfy_server.strip() or settings.default_ntfy_server
     full_title = f"{msg.source}: {msg.title}" if msg.source else msg.title
 
+    # Per-feed auth wins; otherwise fall back to the default-server credentials.
+    has_feed_auth = bool(feed.ntfy_token.strip() or feed.ntfy_username.strip())
+    token = feed.ntfy_token if has_feed_auth else settings.default_ntfy_token
+    username = feed.ntfy_username if has_feed_auth else settings.default_ntfy_username
+    password = feed.ntfy_password if has_feed_auth else settings.default_ntfy_password
+
     # --- ntfy (default channel; requires a topic) ---
     if feed.ntfy_topic.strip():
         try:
@@ -107,9 +113,9 @@ async def dispatch(feed: Feed, settings: Settings, msg: Message) -> DispatchResu
                 tags=feed.tags,
                 priority=feed.priority,
                 attach=msg.image if feed.attach_image else "",
-                token=feed.ntfy_token,
-                username=feed.ntfy_username,
-                password=feed.ntfy_password,
+                token=token,
+                username=username,
+                password=password,
             )
             result.channels.append("ntfy")
         except Exception as exc:  # noqa: BLE001
@@ -146,6 +152,9 @@ async def send_admin_alert(settings: Settings, text: str) -> None:
             message=text,
             tags="warning",
             priority=4,
+            token=settings.default_ntfy_token,
+            username=settings.default_ntfy_username,
+            password=settings.default_ntfy_password,
         )
     except Exception as exc:  # noqa: BLE001
         log.warning("admin alert failed: %s", exc)