fix: reduce db pool size to prevent connection exhaustion, sort grouped views by count

Pool was 20+10 overflow per engine; uvicorn --reload leaked pools until
Postgres hit max_connections=100. Reduced to 5+5 with pool_pre_ping.

Grouped views (tags, people, colors, rated) now sort cards largest-first.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/people/PeopleView.tsx

@@ -1,4 +1,4 @@
-import { useState, useCallback } from 'react'
+import { useState, useCallback, useMemo } from 'react'
 import { Users, Pencil, Check, X, Loader2, ArrowLeft } from 'lucide-react'
 import clsx from 'clsx'
 import { useMutation, useQueryClient } from '@tanstack/react-query'
@@ -19,7 +19,11 @@ import { toast } from '../ToastContainer'
  * 2. Detail view showing a person's photos in the full Timeline — Esc to go back
  */
 export function PeopleView() {
-  const { data: clusters = [], isLoading } = useTagsQuery('face_cluster')
+  const { data: rawClusters = [], isLoading } = useTagsQuery('face_cluster')
+  const clusters = useMemo(
+    () => [...rawClusters].sort((a, b) => b.photo_count - a.photo_count),
+    [rawClusters]
+  )
   const queryClient = useQueryClient()
   const setTagIds = useFilterStore((s) => s.setTagIds)