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/Util/Alerts.swift

@@ -94,33 +94,6 @@ enum RecipeAlert: UserAlert {
 }
 
 
-enum RecipeImportAlert: UserAlert {
-    case BAD_URL,
-         CHECK_CONNECTION,
-         WEBSITE_NOT_SUPPORTED
-    
-    var localizedDescription: LocalizedStringKey {
-        switch self {
-        case .BAD_URL: return "Please check the entered URL."
-        case .CHECK_CONNECTION: return "Unable to load website content. Please check your internet connection."
-        case .WEBSITE_NOT_SUPPORTED: return "This website might not be currently supported. If this appears incorrect, you can use the support options in the app settings to raise awareness about this issue."
-        }
-    }
-    
-    var localizedTitle: LocalizedStringKey {
-        switch self {
-        case .BAD_URL: return "Bad URL"
-        case .CHECK_CONNECTION: return "Connection error"
-        case .WEBSITE_NOT_SUPPORTED: return "Parsing error"
-        }
-    }
-    
-    var alertButtons: [AlertButton] {
-        return [.OK]
-    }
-}
-
-
 enum RequestAlert: UserAlert {
     case REQUEST_DELAYED,
          REQUEST_DROPPED,