Modernize networking layer and fix category navigation and recipe list bugs

Network layer:
- Replace static CookbookApi protocol with instance-based CookbookApiProtocol
  using async/throws instead of tuple returns
- Refactor ApiRequest to use URLComponents for proper URL encoding, replace
  print statements with OSLog, and return typed NetworkError cases
- Add structured NetworkError variants (httpError, connectionError, etc.)
- Remove global cookbookApi constant in favor of injected dependency on AppState
- Delete unused RecipeEditViewModel, RecipeScraper, and Scraper playground

Data & model fixes:
- Add custom Decodable for RecipeDetail with safe fallbacks for malformed JSON
- Make Category Hashable/Equatable use only `name` so NavigationSplitView
  selection survives category refreshes with updated recipe_count
- Return server-assigned ID from uploadRecipe so new recipes get their ID
  before the post-upload refresh block executes

View updates:
- Refresh both old and new category recipe lists after upload when category
  changes, mapping empty recipeCategory to "*" for uncategorized recipes
- Raise deployment target to iOS 18, adopt new SwiftUI API conventions
- Clean up alerts, onboarding views, and settings

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

Nextcloud Cookbook iOS Client/Data/DataModels.swift

@@ -20,6 +20,14 @@ struct Category: Codable {
 
 extension Category: Identifiable, Hashable {
     var id: String { name }
+
+    static func == (lhs: Category, rhs: Category) -> Bool {
+        lhs.name == rhs.name
+    }
+
+    func hash(into hasher: inout Hasher) {
+        hasher.combine(name)
+    }
 }