Add category and recipe sorting with multiple modes and order inversion

Categories on the main page can be sorted by Recently Used, Alphabetical,
or Manual (drag-to-reorder). The sort menu appears inline next to the
Categories header. All Recipes is included in the sort order and manual
reorder sheet. Recipes within category and all-recipes lists can be sorted
by Recently Added or Alphabetical, with the sort button in the toolbar.
All non-manual sort modes support order inversion via a Reverse/Default
Order toggle. Date parsing handles both formatted strings and Unix
timestamps, with recipe_id as fallback when dates are unavailable.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Nextcloud Cookbook iOS Client/Data/CategorySortMode.swift

@@ -0,0 +1,55 @@
+//
+//  CategorySortMode.swift
+//  Nextcloud Cookbook iOS Client
+//
+
+import Foundation
+
+enum CategorySortMode: String, CaseIterable {
+    case recentlyUsed = "recentlyUsed"
+    case alphabetical = "alphabetical"
+    case manual = "manual"
+
+    func descriptor() -> String {
+        switch self {
+        case .recentlyUsed: return String(localized: "Recently Used")
+        case .alphabetical: return String(localized: "Alphabetical")
+        case .manual: return String(localized: "Manual")
+        }
+    }
+
+    var iconName: String {
+        switch self {
+        case .recentlyUsed: return "clock"
+        case .alphabetical: return "textformat.abc"
+        case .manual: return "line.3.horizontal"
+        }
+    }
+
+    var supportsInvert: Bool {
+        self != .manual
+    }
+
+    static let allValues: [CategorySortMode] = CategorySortMode.allCases
+}
+
+enum RecipeSortMode: String, CaseIterable {
+    case recentlyAdded = "recentlyAdded"
+    case alphabetical = "alphabetical"
+
+    func descriptor() -> String {
+        switch self {
+        case .recentlyAdded: return String(localized: "Recently Added")
+        case .alphabetical: return String(localized: "Alphabetical")
+        }
+    }
+
+    var iconName: String {
+        switch self {
+        case .recentlyAdded: return "clock"
+        case .alphabetical: return "textformat.abc"
+        }
+    }
+
+    static let allValues: [RecipeSortMode] = RecipeSortMode.allCases
+}