fix(missions): swap cache:no-store for query cache-buster (hang fix)

fetch(url, { cache: no-store }) was hanging forever through the
edge proxy on the mission API endpoints — requests never reached
postgres and the client-side loading state was stuck true, making
Refresh appear broken. Regressed in d42398d.

Switch to a per-request _t=Date.now() query param on GETs — same
cache-defeat effect, doesn't change fetch semantics.

frontend/src/lib/api/missions.ts

@@ -174,12 +174,14 @@ export interface CreateMissionRequest {
 }
 
 async function api<T>(path: string, init?: RequestInit): Promise<T> {
-  // Missions endpoints are mutable state (statuses transition every
+  // Missions endpoints are mutable state. We bypass browser cache
-  // few seconds) so we always bypass the browser cache. The old cache
+  // via a per-request `_t` query param rather than fetch's `cache:
-  // heuristic could serve a stale response for the manual Refresh
+  // "no-store"` mode, which appears to hang forever through the
-  // click, making it look like a no-op.
+  // edge proxy for reasons TBD.
-  const r = await fetch(path, {
+  const method = init?.method ?? "GET";
-    cache: "no-store",
+  const busted =
+    method === "GET" ? `${path}${path.includes("?") ? "&" : "?"}_t=${Date.now()}` : path;
+  const r = await fetch(busted, {
     ...init,
     headers: {
       "Content-Type": "application/json",