refactor(runtimes): split monolithic page, add zustand store, time range selector, and delete support

- Split 1189-line runtimes-page.tsx into focused sub-components (list, detail, ping, usage, 5 chart files, shared UI, utils)
- Add useRuntimeStore zustand store for shared runtime state across pages (agents page now uses it too)
- Add 7d/30d/90d time range selector to usage charts
- Add full-stack runtime delete: SQL query, Go handler, API route, frontend with confirmation dialog
- Remove unused daemon:heartbeat WS listener (server never broadcasts it)

apps/web/shared/api/client.ts

@@ -283,6 +283,10 @@ export class ApiClient {
     return this.fetch(`/api/runtimes/${runtimeId}/activity`);
   }
 
+  async deleteRuntime(runtimeId: string): Promise<void> {
+    await this.fetch(`/api/runtimes/${runtimeId}`, { method: "DELETE" });
+  }
+
   async pingRuntime(runtimeId: string): Promise<RuntimePing> {
     return this.fetch(`/api/runtimes/${runtimeId}/ping`, { method: "POST" });
   }