fix(web): redirect legacy dashboard routes to the SPA routes

[yyyr-p]

Summary

The dashboard was rebuilt as a React SPA, which moved several routes. Previously bookmarked paths such as /dashboard/keys, /dashboard/requests/:keyId, and /dashboard/upstreams/:id now fall through to the framework 404 page. This adds client-side redirects from the legacy Vue-era paths to their SPA equivalents.

• Add apps/web/src/lib/legacy-redirects.ts, a pure matcher that maps legacy absolute paths — including dynamic params and the old #record-id hash — to new SPA URLs.
• Register the legacy paths in routes.ts, generating the routes from the rule table so a new mapping only requires a table entry.
• /dashboard/requests/:keyId carries the key over as ?key=, and the old record-selection hash is forwarded as ?record=.
• A thin clientLoader on apps/web/src/routes/legacy-redirects.ts issues the redirect (302) or 404s.

Legacy → new:

legacy	new
/login	/
/dashboard/keys	/dashboard/services/api-keys
/dashboard/models	/dashboard/playground
/dashboard/performance	/dashboard/monitor/performance
/dashboard/requests	/dashboard/monitor/requests
/dashboard/requests/:keyId	/dashboard/monitor/requests?key=:keyId
/dashboard/upstreams	/dashboard/providers/upstreams
/dashboard/upstreams/new[:provider]	/dashboard/providers/upstreams/new[:provider]
/dashboard/upstreams/:id	/dashboard/providers/upstreams/:id
/dashboard/usage	/dashboard/monitor/usage
/dashboard/users	/dashboard/admin/users

Test Plan

• New apps/web/__tests__/lib/legacy-redirects_test.ts covers static mappings, dynamic params, record-hash forwarding, trailing slashes, and unknown paths.
• pnpm --filter @floway-dev/web run typecheck
• pnpm --filter @floway-dev/web run build
• ESLint on changed files