feat(webui): vue admin panel source

Vue 3 + TypeScript + Pinia + Tailwind v4 + shadcn-vue + Chart.js admin
panel source under webui/, built with Vite. Views: Overview (providers,
redis/cache/retry status, model aliases), Usage (per-user/per-group/total
tables with tokensIn/tokensOut/cost + limits), Charts (scope selector,
req/tokens(stacked in-out)/cost metric tabs, 24h/30d/12mo window
switcher, fed by GET /admin/api/usage/history). Pinia stores: auth
(sessionStorage key gate, x-api-key header, 401/403 re-prompt),
dashboard (5s poll), history (fetch-on-selection + 30s refresh).

Design: deliberate neutral warm-neutral palette with a signature teal
accent (no default Inter/purple-gradient/glassmorphism), real
typographic hierarchy via the platform UI/mono font stacks (zero
external assets - no Google Fonts), dark+light via prefers-color-scheme
(no class toggle, no theme switcher). Charts: zero-based bars, honest
axes, Okabe-Ito colorblind-safe series, tokens-in/out as a
distinguishable stacked pair.

vite.config.ts: base '/admin/' (matches admin.go's route layout) and
build.modulePreload.polyfill:false (no inline bootstrap script, so the
tightened admin CSP needs no 'unsafe-inline'). Code-split: Chart.js
(ChartsView) loads lazily, not in the initial bundle.

generate.mjs reads dist/ after `vite build` and writes
../admin_assets_gen.go (not committed by this change) - base64-encodes
every asset, decoded once at package-var init; documented rationale in
the script's own header comment.

Hygiene: webui/go.mod walls webui/ off from the repo root's `go build`/
`vet`/`test ./...` (npm's node_modules bundles a stray .go file that
would otherwise be swept in); tools/yaegi-check/main.go excludes webui/
from its GOPATH copy for the same reason. webui/ export-ignored
(.gitattributes) from release source tarballs; webui/node_modules/
gitignored. tsconfig.app.json/tsconfig.node.json's JSONC comments
dropped (TS itself is fine with either; the global pre-commit JSON
validator is not) - no config values changed.

webui/src/components/UsageView.vue

@@ -0,0 +1,84 @@
+<script setup lang="ts">
+import { computed } from 'vue'
+
+import { Card, CardContent, CardDescription, CardHeader, CardTitle } from '@/components/ui/card'
+import UsageTable from '@/components/UsageTable.vue'
+import { formatCost } from '@/lib/format'
+import { useDashboardStore } from '@/stores/dashboard'
+import type { AdminUsageEntryView } from '@/types/api'
+
+const dashboard = useDashboardStore()
+const usage = computed(() => dashboard.usage)
+
+/** memberCounts maps a group name to its member count — only the Overview response carries it. */
+const memberCounts = computed<Record<string, number>>(() => {
+  const out: Record<string, number> = {}
+  for (const g of dashboard.overview?.groups ?? []) out[g.name] = g.memberCount
+  return out
+})
+
+function groupNameOf(entry: AdminUsageEntryView): string {
+  return entry.groupName ?? ''
+}
+function memberCountOf(entry: AdminUsageEntryView): string {
+  const count = memberCounts.value[entry.id]
+  return count === undefined ? '' : String(count)
+}
+</script>
+
+<template>
+  <div class="flex flex-col gap-6">
+    <Card v-if="usage">
+      <CardHeader>
+        <CardTitle>Total</CardTitle>
+        <CardDescription>Usage summed across every user and group combined.</CardDescription>
+      </CardHeader>
+      <CardContent class="grid grid-cols-2 gap-4 text-sm sm:grid-cols-4">
+        <div>
+          <p class="text-muted-foreground">Requests/day</p>
+          <p class="text-lg font-semibold tabular-nums">{{ usage.total.requestsPerDay }}</p>
+        </div>
+        <div>
+          <p class="text-muted-foreground">Tokens in/day</p>
+          <p class="text-lg font-semibold tabular-nums">{{ usage.total.tokensInPerDay }}</p>
+        </div>
+        <div>
+          <p class="text-muted-foreground">Tokens out/day</p>
+          <p class="text-lg font-semibold tabular-nums">{{ usage.total.tokensOutPerDay }}</p>
+        </div>
+        <div>
+          <p class="text-muted-foreground">Cost/day</p>
+          <p class="text-lg font-semibold tabular-nums">{{ formatCost(usage.total.costPerDayMicroUsd) }}</p>
+        </div>
+      </CardContent>
+    </Card>
+
+    <Card>
+      <CardHeader>
+        <CardTitle>Groups</CardTitle>
+      </CardHeader>
+      <CardContent>
+        <UsageTable
+          id-label="Name"
+          secondary-column-label="Members"
+          :entries="usage?.groups ?? []"
+          :secondary-value="memberCountOf"
+        />
+      </CardContent>
+    </Card>
+
+    <Card>
+      <CardHeader>
+        <CardTitle>Users</CardTitle>
+      </CardHeader>
+      <CardContent>
+        <UsageTable
+          id-label="Name"
+          secondary-column-label="Group"
+          :entries="usage?.users ?? []"
+          :secondary-value="groupNameOf"
+        />
+      </CardContent>
+    </Card>
+  </div>
+</template>