refactor: unify Pick with active heap membership

Pick and add-to-heap were two ways of saying "I want to keep this
one". Merging them: P now toggles the selection's membership in the
active heap. The is_picked flag goes away (orphaned in the DB the
same way is_trashed was).

Backend
- Drop is_picked from PhotoBase / PhotoUpdate / PhotoResponse and
  from the photos list filter param.
- Drop the is_picked Column from the Photo model (DB column stays
  on legacy installs but is no longer read or written).
- Drop the bulk action 'pick' branch.
- New GET /heaps/{id}/photo_ids returns just the flat string list.
  Used by the frontend for fast client-side membership lookups
  without fetching full photo records.

Frontend
- New hooks/useActiveHeapMembersQuery.ts → returns
  { activeHeap, memberIds: Set<string> }. Subscribes once at the
  Timeline level and passes a derived isInActiveHeap bool down to
  each PhotoThumbnail (avoids hundreds of thumbnails subscribing
  to the same query).
- PhotoThumbnail: replaces the old check-icon Pick affordance with
  a clear basket badge in the bottom-right corner — a small filled
  pick-colour pill containing a ShoppingBasket icon — visible only
  when the photo belongs to the active heap.
- P shortcut (useKeyboardShortcuts) now toggles membership: if every
  selected photo is already a member, it removes them; otherwise it
  adds the missing ones. T binding removed (P fully replaces it).
- RightSidebar Pick button is now a Pick / Picked toggle bound to
  the active heap. Disabled with a hint when no heap is active.
  Shows the heap name in its title attr.
- filterStore drops 'picked' and 'unflagged' from FlagFilter.
  FilterBar's flag dropdown is now just Any / Discarded.
- LeftSidebar drops the "Flagged" virtual node (it just set
  flag=picked, which no longer exists).
- KeyboardHints: P → "Pick → heap".
- Photo TS type drops is_picked.

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

frontend/src/components/layout/RightSidebar.tsx

@@ -8,14 +8,16 @@ import {
   Info,
   ChevronDown,
   ChevronRight,
-  Check,
+  ShoppingBasket,
   Trash2,
 } from 'lucide-react'
 import clsx from 'clsx'
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query'
 import { format } from 'date-fns'
 import { usePhotoStore } from '../../store/photoStore'
-import { photos as photosApi } from '../../services/api'
+import { photos as photosApi, heaps as heapsApi } from '../../services/api'
+import { useActiveHeapMembers } from '../../hooks/useActiveHeapMembersQuery'
+import { HEAPS_QUERY_KEY } from '../../hooks/useHeapsQuery'
 
 interface PhotoDetails {
   id: string
@@ -26,7 +28,6 @@ interface PhotoDetails {
   file_size: number | null
   taken_at: string | null
   rating: number
-  is_picked: boolean
   is_discarded: boolean
   user_title: string | null
   user_notes: string | null
@@ -122,7 +123,6 @@ export function RightSidebar() {
   const updateMutation = useMutation({
     mutationFn: (data: {
       rating?: number
-      is_picked?: boolean
       is_discarded?: boolean
       user_title?: string | null
       user_notes?: string | null
@@ -134,6 +134,29 @@ export function RightSidebar() {
     },
   })
 
+  // Membership in the active heap (for the Pick toggle button).
+  const { activeHeap, memberIds: activeHeapMembers } = useActiveHeapMembers()
+  const isInActiveHeap =
+    !!activePhotoId && activeHeapMembers.has(activePhotoId)
+
+  const heapMutation = useMutation({
+    mutationFn: ({ remove }: { remove: boolean }) => {
+      if (!activeHeap || !activePhotoId) return Promise.resolve(null)
+      return remove
+        ? heapsApi.removePhotos(activeHeap.id, [activePhotoId])
+        : heapsApi.addPhotos(activeHeap.id, [activePhotoId])
+    },
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: HEAPS_QUERY_KEY })
+      if (activeHeap) {
+        queryClient.invalidateQueries({
+          queryKey: ['heap-photo-ids', activeHeap.id],
+        })
+      }
+      queryClient.invalidateQueries({ queryKey: ['photos'] })
+    },
+  })
+
   // Local drafts for the editable text fields. These mirror the server value
   // but stay independent while the user is typing, so we don't fight focus or
   // clobber edits with stale refetches.
@@ -178,7 +201,6 @@ export function RightSidebar() {
 
   const multipleSelected = selectedPhotos.length > 1
   const rating = photo?.rating ?? 0
-  const isPicked = photo?.is_picked ?? false
   const isDiscarded = photo?.is_discarded ?? false
   const colorLabel = (photo?.color_label ?? null) as ColorLabel | null
 
@@ -299,28 +321,28 @@ export function RightSidebar() {
             <label className="mb-1 block text-xs text-text-muted">Flag</label>
             <div className="flex gap-2">
               <button
-                onClick={() =>
-                  updateMutation.mutate({
-                    is_picked: !isPicked,
-                    is_discarded: false,
-                  })
-                }
+                onClick={() => heapMutation.mutate({ remove: isInActiveHeap })}
+                disabled={!activeHeap || heapMutation.isPending}
                 className={clsx(
-                  'flex items-center gap-1 rounded px-2 py-1 text-sm transition-colors',
-                  isPicked
+                  'flex items-center gap-1 rounded px-2 py-1 text-sm transition-colors disabled:cursor-not-allowed disabled:opacity-50',
+                  isInActiveHeap
                     ? 'bg-pick/20 text-pick'
                     : 'bg-surface-2 text-text-muted hover:bg-surface-offset'
                 )}
+                title={
+                  activeHeap
+                    ? isInActiveHeap
+                      ? `Remove from "${activeHeap.name}"`
+                      : `Add to "${activeHeap.name}"`
+                    : 'Set an active heap first'
+                }
               >
-                <Check className="h-3 w-3" />
-                Pick
+                <ShoppingBasket className="h-3 w-3" />
+                {isInActiveHeap ? 'Picked' : 'Pick'}
               </button>
               <button
                 onClick={() =>
-                  updateMutation.mutate({
-                    is_discarded: !isDiscarded,
-                    is_picked: false,
-                  })
+                  updateMutation.mutate({ is_discarded: !isDiscarded })
                 }
                 className={clsx(
                   'flex items-center gap-1 rounded px-2 py-1 text-sm transition-colors',