feat(mobile): UI-03 forms and collaboration pages (09-12)

- Page 09 create: grouped form (Event details / Description & languages),
  required default-language selector, zh-CN/en tabs with per-locale
  title/description/venue/address, explicit timezone field, bottom save
  button kept keyboard-reachable, create mode has no Access tab
- Page 10 edit: Details/Access tabs sharing one draft; Access has four
  switches with explanations; original downloads constrained by downloads
  (disabled + forced off in PATCH); unsaved-changes PopScope confirm;
  save commits all changes in one minimal PATCH
- Page 11 members: Owner group + Collaborators list with initial avatars
  and per-row remove; full-width Invite colleague opens account-search
  bottom sheet (debounced prefix search, race guard, already-added state);
  remove confirm names the member
- Page 12 categories: extracted to standalone page with per-row edit/
  delete menu and New category sheet (language tabs + name + sort order);
  delete confirm mentions photo impact; collaborator browse-only; old
  inline section removed from album detail
- l10n: new form/members/categories keys both locales; regenerated
- tests: form 14, members 6, categories 7, detail nav 1; full suite green

Co-Authored-By: Claude Code <noreply@anthropic.com>

apps/mobile/lib/l10n/app_en.arb

@@ -66,28 +66,40 @@
   "albumsEmpty": "No albums yet. Tap \"Create album\" to get started",
   "loadMoreFailed": "Failed to load more. Tap to retry",
   "albumCreate": "Create album",
-  "albumEdit": "Edit album",
-  "albumSectionEventInfo": "Event info",
-  "albumSectionContent": "Multilingual content",
-  "albumSectionAccess": "Access settings",
   "albumTitle": "Title",
   "albumDescription": "Description",
   "albumVenue": "Venue",
   "albumAddress": "Address",
-  "albumDefaultLocale": "Default locale",
   "albumStartAt": "Start time",
   "albumEndAtOptional": "End time (optional)",
   "clearEndAt": "Clear end time",
   "albumTimezone": "Timezone",
   "albumTimezoneInvalid": "Invalid IANA timezone name",
-  "switchUpload": "Allow uploads",
-  "switchPublic": "Publicly visible",
-  "switchDownload": "Allow downloads",
-  "switchOriginalDownload": "Allow original downloads",
   "formStartAtRequired": "Pick a start time",
   "formDefaultLocaleMissing": "Default locale must have a title",
   "formTitleRequiredWithFields": "Title is required when description, venue or address is filled",
   "formEndAtNotAfterStartAt": "End time must be after start time",
+  "formEventDetails": "Event details",
+  "formDescriptionLanguages": "Description & languages",
+  "formDefaultLanguage": "Default language",
+  "formDetailsTab": "Details",
+  "formAccessTab": "Access",
+  "formAllowUploads": "Allow uploads",
+  "formAllowUploadsDesc": "Allow staff to upload photos to this album",
+  "formPublicAccess": "Public access",
+  "formPublicAccessDesc": "Anyone with the link can view photos",
+  "formAllowDownloads": "Allow downloads",
+  "formAllowDownloadsDesc": "Viewers can download browse-quality photos",
+  "formOriginalDownloads": "Original downloads",
+  "formOriginalDownloadsDesc": "Viewers can download original photos",
+  "createAlbumTitle": "Create album",
+  "createAlbumSubmit": "Create album",
+  "editAlbumTitle": "Edit album",
+  "saveChanges": "Save changes",
+  "unsavedChangesTitle": "Discard changes?",
+  "unsavedChangesBody": "Your edits are not saved yet. Leaving now will discard them.",
+  "discardChanges": "Discard",
+  "keepEditing": "Keep editing",
   "create": "Create",
   "save": "Save",
   "albumStatusActive": "Active",
@@ -98,27 +110,36 @@
   "tagOriginal": "Original",
   "notSet": "Not set",
   "actionEdit": "Edit",
-  "albumMembers": "Members",
+  "membersTitle": "Members",
+  "membersTitleCount": "Members ({count})",
+  "@membersTitleCount": { "placeholders": { "count": { "type": "int" } } },
+  "ownerGroup": "Owner",
+  "collaboratorsGroup": "Collaborators",
+  "noCollaborators": "No collaborators yet",
+  "inviteColleague": "Invite colleague",
+  "alreadyAdded": "Already added",
+  "add": "Add",
+  "categoriesTitle": "Categories",
+  "newCategory": "New category",
+  "editCategory": "Edit category",
+  "deleteCategoryConfirm": "Delete \"{name}\"? Its photos will become uncategorized.",
+  "@deleteCategoryConfirm": { "placeholders": { "name": { "type": "String" } } },
+  "noCategories": "No categories yet",
   "albumCategories": "Categories",
   "shareQrTitle": "Share QR code",
   "albumPhotos": "Photos",
   "delete": "Delete",
-  "deleteConfirmCategory": "Delete this category? Its photos will become uncategorized.",
-  "categoryEmpty": "No categories yet. Tap + to add one",
-  "categoryAdd": "Add category",
-  "categoryEdit": "Edit category",
   "categoryNameZh": "Chinese name",
   "categoryNameEn": "English name",
   "categorySortOrder": "Sort order",
   "categoryNameRequired": "At least one language name is required",
   "categorySortOrderInvalid": "Sort order must be an integer",
-  "albumMembersEmpty": "No members yet",
   "inviteSearchHint": "Search by account prefix to invite (at least 2 characters)",
   "inviteNoResults": "No matching users",
-  "invite": "Invite",
   "memberInvited": "Invited",
   "removeMember": "Remove member",
-  "removeMemberConfirm": "Remove this member?",
+  "removeMemberConfirm": "Remove {name} from this album?",
+  "@removeMemberConfirm": { "placeholders": { "name": { "type": "String" } } },
   "roleOwner": "Owner",
   "roleCollaborator": "Collaborator",
   "selfMarker": " (you)",