feat(console): replace management UI with operator control plane

[ian-pascoe]

Summary

• replace the placeholder /console frontend with a routed operator control plane spanning overview, setup, providers, models, config, system, access, and observability workflows
• add internal management summary endpoints plus safer bootstrap, asset-serving, packaging, and docs updates so the Go server can ship the built console reliably
• preserve operator-critical workflows for config editing, auth files, OAuth/quota, logs, usage, and system controls while adding route tests and parity checklist coverage

Verification

• pnpm --filter console test -- src/routes/access/page.test.tsx src/routes/observability/page.test.tsx src/app/router.test.tsx src/routes/providers/page.test.tsx src/routes/models/page.test.tsx src/routes/overview/page.test.tsx src/routes/setup/page.test.tsx src/routes/config/page.test.tsx src/routes/access/queries.test.ts src/lib/management-client.test.ts
• pnpm --filter console typecheck
• pnpm --filter console build
• pnpm build
• go test ./internal/api/handlers/management/...
• go test ./internal/api -run 'TestConsoleRoute|TestManagementHTML|TestHealthz|TestManagementSummaryRoutes|TestUpdateClients_KeepsManagementRoutesEnabledWithLocalPassword|TestManagementRoutesAcceptLocalPasswordWithoutRemoteKey|TestManagementRoutesFailedAttemptsUseRemoteAddrInsteadOfForwardedFor' -count=1