feat: copper accent theme, always-expanded group filter, app icon; rename MyPass to KeeVault

- Custom copper AccentColor and warm VaultBackground color assets (light/dark),
  applied to both the main app and the AutoFill extension (which needed its own
  copy of the asset catalog plus ASSETCATALOG_COMPILER_GLOBAL_ACCENT_COLOR_NAME
  and an explicit .tint() modifier, since extensions don't pick up the app-wide
  accent color the same way a full SwiftUI App/Scene does).
- GroupFilterView no longer uses DisclosureGroup for subgroups -- the whole tree
  renders always-expanded (indented per depth) so active filters are visible at
  a glance instead of requiring tap-to-expand.
- Added a placeholder app icon (padlock glyph, light/dark/tinted variants plus
  macOS sizes) -- previously the icon slot existed but had no actual images,
  which blocks App Store/TestFlight archive validation.
- Added ITSAppUsesNonExemptEncryption = NO (standard encryption only, via
  KeePassKit) to skip the export-compliance prompt on each upload.
- Renamed the app from MyPass to KeeVault throughout: Xcode project/targets/
  schemes, the MyPassCore package (now KeeVaultCore) and every import site,
  folder and file names, bundle identifiers (org.antiloop222.keevault) and
  their App Group/Keychain-group entitlements, and remaining UI/string
  references -- MyPass was already taken as an App Store app name.

KeeVault/ViewModels/GroupFilterViewModel.swift

@@ -0,0 +1,33 @@
+import Foundation
+import Combine
+import KeeVaultCore
+
+@MainActor
+final class GroupFilterViewModel: ObservableObject {
+    @Published var selectedGroupIds: Set<UUID> = []
+    /// The group id passed to the most recent `toggle(_:)` call that resulted in a non-empty
+    /// selection, used as a "best effort" default group for new entries. Cleared to `nil`
+    /// whenever a toggle empties the selection, or by `clear()`.
+    @Published private(set) var lastToggledGroupId: UUID?
+
+    private let session: VaultSession
+
+    init(session: VaultSession) {
+        self.session = session
+    }
+
+    func isSelected(_ group: KeeVaultCore.Group) -> Bool {
+        selectedGroupIds.contains(group.id)
+    }
+
+    func toggle(_ group: KeeVaultCore.Group) {
+        guard let root = session.database?.root else { return }
+        selectedGroupIds = GroupSelection.toggling(group.id, in: root, current: selectedGroupIds)
+        lastToggledGroupId = selectedGroupIds.isEmpty ? nil : group.id
+    }
+
+    func clear() {
+        selectedGroupIds = []
+        lastToggledGroupId = nil
+    }
+}