Replace Flutter app with native SwiftUI rewrite (iOS 26)

Complete ground-up rewrite in SwiftUI targeting iOS 26. Drops the Flutter/Dart
codebase entirely in favour of a lean native app with no third-party dependencies.

Features shipped:
- Bookmark list with pagination, pull-to-refresh, swipe delete/archive
- Add bookmark form + iOS share extension (zero-tap save from any app)
- Tags tab — all tags sorted by count, tap to browse filtered bookmarks
- Native search tab (Tab role: .search) with instant client-side filtering
- AI enrichment via OpenRouter (google/gemini-2.0-flash-lite-001): auto-summary
  and tag generation, semantic search, smart collections
- Settings: linkding server config, OpenRouter API key
- App Groups for credential sharing between main app and share extension
- Swift 6 strict concurrency throughout (@Observable, @MainActor)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.metadata

@@ -1,30 +0,0 @@
-# This file tracks properties of this Flutter project.
-# Used by Flutter tool to assess capabilities and perform upgrades etc.
-#
-# This file should be version controlled and should not be manually edited.
-
-version:
-  revision: "00b0c91f06209d9e4a41f71b7a512d6eb3b9c694"
-  channel: "stable"
-
-project_type: app
-
-# Tracks metadata for the flutter migrate command
-migration:
-  platforms:
-    - platform: root
-      create_revision: 00b0c91f06209d9e4a41f71b7a512d6eb3b9c694
-      base_revision: 00b0c91f06209d9e4a41f71b7a512d6eb3b9c694
-    - platform: android
-      create_revision: 00b0c91f06209d9e4a41f71b7a512d6eb3b9c694
-      base_revision: 00b0c91f06209d9e4a41f71b7a512d6eb3b9c694
-
-  # User provided section
-
-  # List of Local paths (relative to this file) that should be
-  # ignored by the migrate tool.
-  #
-  # Files that are not part of the templates will be ignored by default.
-  unmanaged_files:
-    - 'lib/main.dart'
-    - 'ios/Runner.xcodeproj/project.pbxproj'