fix: add top-level GET /workspaces endpoint and derive project/repo from workspace data

- Add all_workspaces_router with GET /workspaces/ (no project/repo required)
- Include project_id in workspace responses
- Frontend: useWorkspaces() calls listAllWorkspaces when no args
- Frontend: WorkspacesPage uses top-level list, derives project/repo from workspace for mutations
- Fixes 422 from invalid UUID path params

apps/web/src/hooks/use-workspaces.ts

@@ -1,7 +1,7 @@
 /** Hook for fetching workspaces. */
 
 import { useCallback, useEffect, useState } from "react";
-import { listWorkspaces } from "../api/workspaces";
+import { listAllWorkspaces, listWorkspaces } from "../api/workspaces";
 import type { Workspace } from "../types/workspace";
 
 export interface UseWorkspacesResult {
@@ -12,8 +12,8 @@ export interface UseWorkspacesResult {
 }
 
 export function useWorkspaces(
-	projectId: string,
-	repoId: string,
+	projectId?: string,
+	repoId?: string,
 ): UseWorkspacesResult {
 	const [workspaces, setWorkspaces] = useState<Workspace[]>([]);
 	const [loading, setLoading] = useState(true);
@@ -23,7 +23,10 @@ export function useWorkspaces(
 		setLoading(true);
 		setError(null);
 		try {
-			const data = await listWorkspaces(projectId, repoId);
+			const data =
+				projectId && repoId
+					? await listWorkspaces(projectId, repoId)
+					: await listAllWorkspaces();
 			setWorkspaces(data);
 		} catch (err) {
 			setError(