feat: dynamic tier limit from backend instead of hardcoded constant (OPE-118)

New useUserUsage hook calls GET /api/v1/users/usage (React Query, 60s stale).
Returns actual max_functions_per_repo for the user's tier from backend.

DashboardHome now passes usage?.limits?.max_functions_per_repo to
DirectoryPicker instead of TIER_FUNCTION_LIMITS[userTier].

Removed: TIER_FUNCTION_LIMITS import, TierName import, rawTier/userTier
derivation from session metadata. All gone from DashboardHome.

If user is on Pro (20K limit), budget bar shows X/20,000.
If admin bumps them to Enterprise (500K), it updates on next page load.
No frontend deploy needed when tier limits change on backend.

Author: DevanshuNEU

frontend/src/components/dashboard/DashboardHome.tsx

@@ -6,7 +6,7 @@ import { useSearchParams } from 'react-router-dom'
 import { AnimatePresence } from 'framer-motion'
 import { toast } from 'sonner'
 import { useAuth } from '../../contexts/AuthContext'
-import { useRepos } from '../../hooks/useCachedQuery'
+import { useRepos, useUserUsage } from '../../hooks/useCachedQuery'
 import { API_URL, MAX_FREE_REPOS } from '../../config/api'
 import { extractErrorMessage, isUpgradeError } from '../../lib/api-errors'
 import { RepoListView } from './RepoListView'
@@ -16,18 +16,14 @@ import { DirectoryPicker } from '../DirectoryPicker'
 import { GitHubRepoSelector } from '../GitHubRepoSelector'
 import { IndexingProgressModal } from '../IndexingProgressModal'
 import { UpgradeLimitModal } from '../UpgradeLimitModal'
-import { TIER_FUNCTION_LIMITS, type TierName } from '../../config/api'
 import type { GitHubRepo } from '../../hooks/useGitHubRepos'
 import type { AnalyzeResult, RepoTab } from '../../types'
 
 export function DashboardHome() {
   const { session } = useAuth()
   const [searchParams, setSearchParams] = useSearchParams()
   const { data: repos = [], isLoading: reposLoading, invalidate: refreshRepos } = useRepos(session?.access_token)
-
-  // User tier -- validate against known tiers, fall back to free for unknown values
-  const rawTier = session?.user?.user_metadata?.tier as string
-  const userTier: TierName = rawTier && rawTier in TIER_FUNCTION_LIMITS ? (rawTier as TierName) : 'free'
+  const { data: usage } = useUserUsage(session?.access_token)
 
   const [selectedRepo, setSelectedRepo] = useState<string | null>(null)
   const [activeTab, setActiveTab] = useState<RepoTab>('overview')
@@ -260,8 +256,7 @@ export function DashboardHome() {
           repoInfo={analyzeResult}
           onConfirm={handleDirectoryConfirm}
           loading={loading}
-          // TODO: replace with actual user tier once GET /users/me returns tier
-          functionLimit={TIER_FUNCTION_LIMITS[userTier]}
+          functionLimit={usage?.limits?.max_functions_per_repo}
         />
       )}
 

frontend/src/hooks/useCachedQuery.ts

@@ -189,3 +189,24 @@ export function useRepos(apiKey: string | undefined) {
 
   return { ...query, invalidate }
 }
+
+
+/** User usage and tier limits from backend -- single source of truth */
+export function useUserUsage(apiKey: string | undefined) {
+  return useQuery({
+    queryKey: ['user', 'usage'],
+    queryFn: async () => {
+      const data = await fetchWithAuth(`${API_URL}/users/usage`, apiKey!)
+      return data as {
+        tier: string
+        limits: {
+          max_files_per_repo: number
+          max_functions_per_repo: number
+          playground_searches_per_day: number | null
+        }
+      }
+    },
+    enabled: !!apiKey,
+    staleTime: 60_000,
+  })
+}