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/Network/NetworkError.swift

@@ -7,17 +7,45 @@
 
 import Foundation
 
-public enum NetworkError: String, Error {
-    case missingUrl = "Missing URL."
-    case parametersNil = "Parameters are nil."
-    case encodingFailed = "Parameter encoding failed."
-    case decodingFailed = "Data decoding failed."
-    case redirectionError = "Redirection error"
-    case clientError = "Client error"
-    case serverError = "Server error"
-    case invalidRequest = "Invalid request"
-    case unknownError = "Unknown error"
-    case dataError = "Invalid data error."
+public enum NetworkError: Error, LocalizedError {
+    case missingUrl
+    case encodingFailed(detail: String? = nil)
+    case decodingFailed(detail: String? = nil)
+    case httpError(statusCode: Int, body: String? = nil)
+    case connectionError(underlying: Error? = nil)
+    case invalidRequest
+    case unknownError(detail: String? = nil)
+
+    public var errorDescription: String? {
+        switch self {
+        case .missingUrl:
+            return "Missing URL."
+        case .encodingFailed(let detail):
+            return "Parameter encoding failed." + (detail.map { " \($0)" } ?? "")
+        case .decodingFailed(let detail):
+            return "Data decoding failed." + (detail.map { " \($0)" } ?? "")
+        case .httpError(let statusCode, let body):
+            return "HTTP error \(statusCode)." + (body.map { " \($0)" } ?? "")
+        case .connectionError(let underlying):
+            return "Connection error." + (underlying.map { " \($0.localizedDescription)" } ?? "")
+        case .invalidRequest:
+            return "Invalid request."
+        case .unknownError(let detail):
+            return "Unknown error." + (detail.map { " \($0)" } ?? "")
+        }
+    }
+
+    var isClientError: Bool {
+        if case .httpError(let statusCode, _) = self {
+            return (400...499).contains(statusCode)
+        }
+        return false
+    }
+
+    var isServerError: Bool {
+        if case .httpError(let statusCode, _) = self {
+            return (500...599).contains(statusCode)
+        }
+        return false
+    }
 }
-
-