fix: use relative Vite base; serve SPA at both /v2/ and /clawstor/

Vite base: '/clawstor/' caused 404s when the SPA was served at /v2/
because asset paths like /clawstor/assets/... didn't match the actual
serve path /v2/assets/...

- vite.config.ts: switch to base: './' (relative paths work from any
  mount point — /v2/, /clawstor/, or bare /)
- serve.rs: mount the SPA at both /v2/ and /clawstor/; add 308 redirect
  from /v2 and /clawstor (no trailing slash) to their canonical forms
  so browsers don't misinterpret the last segment as a filename and
  break relative ./assets/ resolution

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

dashboard-v2/vite.config.ts

@@ -6,13 +6,12 @@ import react from '@vitejs/plugin-react';
 // During local dev the daemon proxies /api/v2/* on :7700 so
 // `vite dev` on :5173 can hit it via server.proxy.
 export default defineConfig({
-  // Absolute base tied to the deploy path. Prior try was `./`
-  // (fully relative) which broke when the user hit `/clawstor`
-  // without trailing slash — browser resolves `./assets/…`
-  // against `/clawstor` treated as a file, gives `/assets/…`,
-  // 404 from Tailscale. Absolute `/clawstor/` sidesteps the
-  // slash / no-slash ambiguity.
-  base: '/clawstor/',
+  // Relative base so the SPA works under any mount point (/v2/,
+  // /clawstor/, or bare /). The no-trailing-slash edge case
+  // (browser treats the path as a file and strips the last segment)
+  // is handled server-side: serve.rs redirects /v2 → /v2/ and
+  // /clawstor → /clawstor/ before serving the SPA.
+  base: './',
   plugins: [react()],
   server: {
     port: 5173,