finish SwiftData migration with @Query views

- Drive chat list, timeline and forward picker from SwiftData @Query
  instead of AppModel's in-memory arrays; inject the per-account
  ModelContext from RootView with an in-memory fallback.
- Physically delete locally deleted messages (context.delete) and
  purge rows marked deleted by older builds on store open, so @Query
  views never resurrect them.
- Delete the legacy JSON snapshot only after a successful import save
  and restore the completeUntilFirstUserAuthentication data protection
  attribute on the store file.
- Mirror the old ChatArchive tolerant decoding in LegacyArchiveImporter
  so snapshots from older schema versions (missing reactions,
  isGroupMessage, roster fields) still import.
- Cover the new behaviour in ArchiveStoreTests and guard it with new
  verify.sh invariants; update AGENTS.md, ARCHITECTURE.md and
  SECURITY.md.

Resources/AppAssets.xcassets/AppIcon.appiconset/Contents.json

@@ -199,6 +199,7 @@
       "size" : "29x29"
     },
     {
+      "filename" : "AppIcon-Watch-Notification-45mm@2x.png",
       "idiom" : "watch",
       "role" : "notificationCenter",
       "scale" : "2x",
@@ -278,6 +279,7 @@
       "subtype" : "44mm"
     },
     {
+      "filename" : "AppIcon-Watch-QuickLook-45mm@2x.png",
       "idiom" : "watch",
       "role" : "quickLook",
       "scale" : "2x",
@@ -285,6 +287,7 @@
       "subtype" : "45mm"
     },
     {
+      "filename" : "AppIcon-Watch-QuickLook-49mm@2x.png",
       "idiom" : "watch",
       "role" : "quickLook",
       "scale" : "2x",