Implementation step

Cookie Auth Domain Models and Preference Storage

Phase 16 Step 16.3 adds the non-secret model layer for opt-in browser cookie auth.

What Changed

Validation

swift test --filter CookieProviderConfigTests --filter CookieAuthPreferencesTests passed.

swift test --filter CookieAuthSettingsViewTests, swift test --filter ProviderConfigurationStoreTests, and swift test --filter SettingsStorageTests passed.

Full swift test still has the expected Step 16.4/16.5 reader red failures because Chrome and Safari cookie parsing/decryption are not implemented in this step.