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/Localizable.xcstrings

@@ -663,6 +663,7 @@
       }
     },
     "Bad URL" : {
+      "extractionState" : "stale",
       "localizations" : {
         "de" : {
           "stringUnit" : {
@@ -931,6 +932,7 @@
       }
     },
     "Connection error" : {
+      "extractionState" : "stale",
       "localizations" : {
         "de" : {
           "stringUnit" : {
@@ -2656,6 +2658,7 @@
       }
     },
     "Parsing error" : {
+      "extractionState" : "stale",
       "localizations" : {
         "de" : {
           "stringUnit" : {
@@ -2722,6 +2725,7 @@
       }
     },
     "Please check the entered URL." : {
+      "extractionState" : "stale",
       "localizations" : {
         "de" : {
           "stringUnit" : {
@@ -3788,6 +3792,7 @@
       }
     },
     "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." : {
+      "extractionState" : "stale",
       "localizations" : {
         "de" : {
           "stringUnit" : {
@@ -4011,6 +4016,7 @@
       }
     },
     "Unable to load website content. Please check your internet connection." : {
+      "extractionState" : "stale",
       "localizations" : {
         "de" : {
           "stringUnit" : {