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/Services/BiometricAuthService.swift

@@ -0,0 +1,23 @@
+//
+//  BiometricAuthService.swift
+//  KeeVault
+//
+
+import LocalAuthentication
+import Foundation
+
+public final class BiometricAuthService {
+    public init() {}
+
+    public var isAvailable: Bool {
+        let ctx = LAContext()
+        var error: NSError?
+        return ctx.canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error: &error)
+    }
+
+    /// Returns true on success. On failure, throws an error with a localized message.
+    public func authenticate(reason: String) async throws {
+        let ctx = LAContext()
+        try await ctx.evaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, localizedReason: reason)
+    }
+}