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.

README.md

@@ -839,15 +839,21 @@ or in CI.
 - **Response headers**: all three JSON routes set
   `X-Content-Type-Options: nosniff` and `Cache-Control: no-store`; every
   hashed asset sets `X-Content-Type-Options: nosniff` and its own
-  immutable `Cache-Control` (above). `GET /admin` and the three JSON
-  routes share one `Content-Security-Policy` header (`default-src 'none';
-  script-src 'self'; style-src 'self'; connect-src 'self'; img-src 'self'
-  data:; frame-ancestors 'none'; base-uri 'none'; form-action 'none'`) —
-  no `'unsafe-inline'`, since the built app has no inline script or style
-  of any kind, only external `/admin/assets/*` references; `img-src`
-  additionally allows `data:` for the page's inlined favicon. The
-  dashboard loads no external asset of any kind and works in an
-  air-gapped cluster.
+  immutable `Cache-Control` (above). Every one of the four routes — `GET
+  /admin`, every hashed asset, and the three JSON routes — shares one
+  `Content-Security-Policy` header (`default-src 'none'; script-src
+  'self'; style-src 'self'; connect-src 'self'; img-src 'self' data:;
+  frame-ancestors 'none'; base-uri 'none'; form-action 'none'`) — no
+  `'unsafe-inline'`, since the built app has no inline script or style of
+  any kind, only external `/admin/assets/*` references; `img-src`
+  additionally allows `data:` for the page's inlined favicon. A browser
+  only enforces CSP against the top-level document that names it, so an
+  asset response's own header governs nothing when the browser fetched it
+  as a `<script src>`/`<link>` sub-resource of `GET /admin` — it matters
+  only if that asset URL is ever navigated to directly, and every other
+  admin route already sends the identical header, so there is no reason
+  for asset responses to be the exception. The dashboard loads no
+  external asset of any kind and works in an air-gapped cluster.
 
 ## MCP and A2A