fix(webui): version display, CSP guards, config traps, bucket-aligned stacking

Review fix round (4 Important + 2 folded):

1. Version display: OverviewView.vue was missing the muted version line
   the old vanilla-JS page rendered (types/api.ts already declared
   overview.version) - added.

2. CSP invariant now guarded twice: webui/generate.mjs's new
   assertNoInlineAssets fails the build if dist/index.html contains an
   inline <script> (no src= attribute) or any <style> tag - the exact
   condition the tightened admin CSP (script-src/style-src 'self', no
   'unsafe-inline') depends on. admin_test.go's new
   TestAdminIndexHTML_NoInlineAssets re-asserts the identical invariant
   server-side, against the decoded adminIndexHTML admin.go actually
   serves, so a regression is caught even if admin_assets_gen.go were
   regenerated with a modified copy of generate.mjs.

3. webui/components.json's iconLibrary:"lucide"/font:"inter" fields
   cannot be fixed in place - checked shadcn-vue's own schema
   (PRESET_ICON_LIBRARIES/PRESET_FONTS in the installed package): no
   "none"/fontawesome/system choice exists for either, and JSON (unlike
   the tsconfig.*.json files touched in the previous commit) has no
   comment syntax to warn inline. Documented instead: webui/README.md
   gained a loud warning section naming the exact regression (already
   hit twice this branch - a re-added Google Fonts import, a re-added
   lucide icon import) and the two-step fix to apply after any future
   shadcn-vue add/init call.

4. Real-CSP verification: the browser pass earlier in this branch ran
   under vite preview, which sends no CSP header at all. New
   integration/integration_test.go: TestAdminAssetCSP fetches GET
   /admin against the real Traefik+Yaegi pipeline, extracts the asset
   URL from its <script src="..."> tag, fetches that asset, and asserts
   both responses carry the exact adminCSP string byte-for-byte.
   admin.go's serveAdminAsset now also sets Content-Security-Policy
   (previously JSON/page routes only) so this holds for a direct
   navigation to an asset URL, not just as a same-origin sub-resource of
   GET /admin; admin_test.go's TestAdminAsset_Serving updated to match.

5. (folded) UsageChart.vue stacked the "tokens" tab's two series
   (tokin/tokout - two separate HTTP requests, not one atomic call) by
   positional index. A window rollover landing between the two requests
   could leave one series one bucket ahead, mis-stacking that refresh.
   Now aligns both series by their bucket key (a sorted union of every
   active series' buckets - the fixed-width, zero-padded bucket strings
   sort chronologically by construction), with a missing bucket in one
   series reading as 0 rather than shifting the whole series.

6. (folded) AuthGate.vue now triggers an immediate dashboard.refresh()
   on successful key submit, instead of waiting up to 5s for the next
   poll tick - the dashboard no longer sits blank right after auth.

Rebuilt via make admin-ui; admin_assets_gen.go regenerated.

admin.go

@@ -160,7 +160,14 @@ func (g *Gateway) serveAdminPage(w http.ResponseWriter) {
 // produces new filenames, never mutates one this browser may have cached.
 // X-Content-Type-Options: nosniff matches the JSON routes' own header
 // (setAdminJSONHeaders) — the declared Content-Type must never be
-// second-guessed by the browser's MIME sniffer.
+// second-guessed by the browser's MIME sniffer. Content-Security-Policy
+// carries adminCSP too (review sweep): a browser only enforces CSP
+// against the top-level document that names it, so this header governs
+// nothing for a JS/CSS response fetched as a sub-resource of GET
+// /admin — but a browser navigated STRAIGHT to an asset URL (a pasted
+// link, a bookmark) treats that response as its own top-level document,
+// and every other admin route already sends the identical header, so
+// there is no reason for this one route to be the exception.
 func (g *Gateway) serveAdminAsset(w http.ResponseWriter, name string) {
 	asset, ok := adminAssets[name]
 	if !ok {
@@ -170,6 +177,7 @@ func (g *Gateway) serveAdminAsset(w http.ResponseWriter, name string) {
 	w.Header().Set("Content-Type", asset.contentType)
 	w.Header().Set("X-Content-Type-Options", "nosniff")
 	w.Header().Set("Cache-Control", "public, max-age=31536000, immutable")
+	w.Header().Set("Content-Security-Policy", adminCSP)
 	_, _ = w.Write(asset.body)
 }