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>

CLAUDE.md

@@ -108,3 +108,7 @@ Four languages supported via `Localizable.xcstrings`: English, German, Spanish,
 - Server credentials (username, token, authString) are stored in `UserDefaults` via `UserSettings`, not in Keychain.
 - No `.gitignore` file exists in the repository.
 - No CI/CD, no linting tools, and no meaningful test coverage.
+
+## Workflow
+
+- Do not run `xcodebuild` directly. Ask the user to build manually in Xcode and report the results back.