feat: remove legacy alert rules, superseded by automations

Alert rules already auto-migrate into automations on boot and the old
engine stands down after. Deletes the rule/firing tables, routes, UI,
and AI tools; keeps notification channels since automations still use
them. Also fixes automations' notify step, which still called the
deleted repository.

src/ui/shell/tabUtils.tsx

@@ -25,7 +25,6 @@ import {
   Fingerprint,
   Hammer,
   Play,
-  Plug,
   ScrollText,
   Sparkles,
   Presentation,
@@ -154,9 +153,6 @@ const FleetInventoryTab = lazy(() =>
 const TermixIdPanel = lazy(() =>
   import("@/sidebar/TermixIdPanel").then((m) => ({ default: m.TermixIdPanel })),
 );
-const AlertsPanel = lazy(() =>
-  import("@/sidebar/AlertsPanel").then((m) => ({ default: m.AlertsPanel })),
-);
 const SessionLogsPanel = lazy(() =>
   import("@/sidebar/SessionLogsPanel").then((m) => ({
     default: m.SessionLogsPanel,
@@ -391,8 +387,6 @@ export function tabIcon(type: TabType) {
       return <Presentation className="size-3.5" />;
     case "termix-id":
       return <Fingerprint className="size-3.5" />;
-    case "alerts":
-      return <Plug className="size-3.5" />;
     case "session-logs":
       return <ScrollText className="size-3.5" />;
     case "snippets":
@@ -721,13 +715,6 @@ export function renderTabContent(
         </PanelTabFrame>,
       );
 
-    case "alerts":
-      return withTabSuspense(
-        <PanelTabFrame>
-          <AlertsPanel />
-        </PanelTabFrame>,
-      );
-
     case "session-logs":
       return withTabSuspense(
         <PanelTabFrame>