[backport cloud/1.37] feat: add workspace session, auth, and store infrastructure (#8230)

## Summary
- Backport of #8194 to cloud/1.37
- Adds workspace session, auth, and store infrastructure for team
workspaces

## Test plan
- [ ] Verify workspace session management works correctly
- [ ] Verify team workspace store initializes properly

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┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8230-backport-cloud-1-37-feat-add-workspace-session-auth-and-store-infrastructure-2f06d73d365081aea34df344a5ce8249)
by [Unito](https://www.unito.io)

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

src/platform/auth/workspace/workspaceConstants.ts

@@ -1,7 +1,10 @@
 export const WORKSPACE_STORAGE_KEYS = {
+  // sessionStorage keys (cleared on browser close)
   CURRENT_WORKSPACE: 'Comfy.Workspace.Current',
   TOKEN: 'Comfy.Workspace.Token',
-  EXPIRES_AT: 'Comfy.Workspace.ExpiresAt'
+  EXPIRES_AT: 'Comfy.Workspace.ExpiresAt',
+  // localStorage key (persists across browser sessions)
+  LAST_WORKSPACE_ID: 'Comfy.Workspace.LastWorkspaceId'
 } as const
 
 export const TOKEN_REFRESH_BUFFER_MS = 5 * 60 * 1000