fix: address PR review -- a11y, tier limit, backdrop guard

5 findings verified and fixed:

1. AddRepoForm close button: add aria-label='Close' for screen readers
2. AddRepoForm backdrop: use isBusy (loading || analyzing) guard instead
   of just loading -- prevents dismissal during analyze API call
3. DirectoryPicker close button: add aria-label='Close'
4. DirectoryPicker props: add functionLimit to interface (was destructured
   but missing from type definition)
5. DashboardHome: derive userTier from session metadata with 'free' fallback
   instead of hardcoded TIER_FUNCTION_LIMITS.free

Skipped: TierName move to types.ts -- type derives from TIER_FUNCTION_LIMITS
via keyof typeof, colocating with the constant is cleaner than re-exporting.

Build passes.

Author: DevanshuNEU

frontend/src/components/AddRepoForm.tsx

@@ -91,7 +91,7 @@ export function AddRepoForm({ onAdd, onAnalyzed, loading, isOpen, onOpenChange }
             animate={{ opacity: 1 }}
             exit={{ opacity: 0 }}
             className="fixed inset-0 bg-background/80 backdrop-blur-md flex items-center justify-center z-50"
-            onClick={() => !loading && setShowForm(false)}
+            onClick={() => !isBusy && setShowForm(false)}
           >
             <motion.div
               initial={{ opacity: 0, scale: 0.95, y: 20 }}
@@ -113,6 +113,7 @@ export function AddRepoForm({ onAdd, onAnalyzed, loading, isOpen, onOpenChange }
                 </div>
                 <button
                   onClick={() => setShowForm(false)}
+                  aria-label="Close"
                   className="w-8 h-8 flex items-center justify-center rounded-lg text-muted-foreground hover:text-foreground hover:bg-muted transition-colors"
                   disabled={isBusy}
                 >

frontend/src/components/DirectoryPicker.tsx

@@ -21,6 +21,7 @@ interface DirectoryPickerProps {
   repoInfo: AnalyzeResult
   onConfirm: (selectedPaths: string[]) => void
   loading: boolean
+  functionLimit?: number
 }
 
 export function DirectoryPicker({
@@ -187,6 +188,7 @@ function PickerHeader({
       <button
         onClick={onClose}
         disabled={loading}
+        aria-label="Close"
         className="w-8 h-8 flex items-center justify-center rounded-lg text-muted-foreground hover:text-foreground hover:bg-muted transition-colors"
       >
         <X className="w-4 h-4" />

frontend/src/components/dashboard/DashboardHome.tsx

@@ -16,7 +16,7 @@ import { DirectoryPicker } from '../DirectoryPicker'
 import { GitHubRepoSelector } from '../GitHubRepoSelector'
 import { IndexingProgressModal } from '../IndexingProgressModal'
 import { UpgradeLimitModal } from '../UpgradeLimitModal'
-import { TIER_FUNCTION_LIMITS } from '../../config/api'
+import { TIER_FUNCTION_LIMITS, type TierName } from '../../config/api'
 import type { GitHubRepo } from '../../hooks/useGitHubRepos'
 import type { AnalyzeResult, RepoTab } from '../../types'
 
@@ -25,6 +25,9 @@ export function DashboardHome() {
   const [searchParams, setSearchParams] = useSearchParams()
   const { data: repos = [], isLoading: reposLoading, invalidate: refreshRepos } = useRepos(session?.access_token)
 
+  // User tier -- defaults to free, will be replaced when user profile API is available
+  const userTier: TierName = (session?.user?.user_metadata?.tier as TierName) || 'free'
+
   const [selectedRepo, setSelectedRepo] = useState<string | null>(null)
   const [activeTab, setActiveTab] = useState<RepoTab>('overview')
   const [loading, setLoading] = useState(false)
@@ -256,7 +259,8 @@ export function DashboardHome() {
           repoInfo={analyzeResult}
           onConfirm={handleDirectoryConfirm}
           loading={loading}
-          functionLimit={TIER_FUNCTION_LIMITS.free}
+          // TODO: replace with actual user tier once GET /users/me returns tier
+          functionLimit={TIER_FUNCTION_LIMITS[userTier]}
         />
       )}