feat(usage): add resource-usage API client, meta hook, and shared utils

The data layer the resource tabs build on:
- apis/resource.ts: adapter over the unified metered_usage read API
  (resource/gpu-instances/storage/summary/events breakdowns), flattening
  the server's generic shape into the per-tab item shape.
- hooks/use-resource-meta.ts: loads creators/instances/volumes filter
  options for the current scope.
- utils/time-buckets.ts: day/week/month/hour bucket keys + range fill.
- utils/export-breakdown.ts: derive Excel columns from antd table specs.

src/pages/usage/hooks/use-resource-meta.ts

@@ -0,0 +1,58 @@
+import { useEffect, useState } from 'react';
+import {
+  queryResourceFilterMeta,
+  ResourceFilterOption
+} from '../apis/resource';
+
+export interface SelectOption {
+  value: number;
+  label: string;
+}
+
+export interface ResourceMetaOptions {
+  creators: SelectOption[];
+  instances: SelectOption[];
+  volumes: SelectOption[];
+}
+
+const EMPTY: ResourceMetaOptions = {
+  creators: [],
+  instances: [],
+  volumes: []
+};
+
+const toOptions = (items: ResourceFilterOption[]): SelectOption[] =>
+  items.map((i) => ({ value: i.id, label: i.label }));
+
+/**
+ * Loads the resource tabs' filter dropdown sources in one call:
+ *   - ``creators``  — "filter by user" (Tokens-tab equivalent of /usage/meta
+ *                     users); only shown to managers, but cheap to always load.
+ *   - ``instances`` — "filter by GPU instance" (GPU Instances tab)
+ *   - ``volumes``   — "filter by volume" (Storage tab)
+ *
+ * Scope-aware: managers get the org-wide lists, others only their own
+ * resources. Refetched when ``scope`` changes.
+ */
+export default function useResourceMeta(
+  scope: 'self' | 'all' = 'all'
+): ResourceMetaOptions {
+  const [meta, setMeta] = useState<ResourceMetaOptions>(EMPTY);
+
+  useEffect(() => {
+    queryResourceFilterMeta(scope)
+      .then((res) =>
+        setMeta({
+          creators: toOptions(res.creators),
+          instances: toOptions(res.instances),
+          volumes: toOptions(res.volumes)
+        })
+      )
+      .catch(() => {
+        // Network/auth errors surface via the global interceptor; leave the
+        // dropdowns empty rather than crashing the tab.
+      });
+  }, [scope]);
+
+  return meta;
+}