feat(ios): establish SwiftUI and generated API foundations

[Tutitoos]

Plan reference

Post-1.0 — iPhone and iPad: native project foundation.

Objective

Create the SwiftUI application, generated OpenAPI client, environment configuration, design tokens, navigation shell, dependency boundaries, and strict Swift 6 concurrency baseline.

Scope

• Add iPhone and iPad targets, package organization, generated client integration, authenticated transport abstraction, localization, error modeling, preview fixtures, CI, and test targets.
• Keep all first-party Swift code inside the monorepo.

Tasks

• Define Swift 6 models, actors, storage, API, and UI boundaries for this scope.
• Implement the smallest complete native capability.
• Add XCTest, Swift Concurrency, migration, UI, accessibility, and device tests where applicable.
• Update generated clients, translations, privacy declarations, and distribution documentation.

Acceptance criteria

• A clean checkout generates the API client and builds both targets without generated diff.

• Strict concurrency checks pass with no blanket unsafe opt-outs.

• The shell renders EN by default, switches to ES, and falls back to EN for missing values.

• No production secret or server URL is embedded in source.

• Account isolation, data protection, accessibility, EN default, and ES completeness match the web and macOS contracts.

• Tokens, credentials, message content, recipients, and personal data never enter logs, crash reports, screenshots, fixtures, URLs, or notification defaults.

• The capability is independently reviewable and rollback-safe.

Validation

• Run clean generation, Swift build, XCTest, localization completeness, iPhone and iPad launch, and CI checks.

• Run Swift build, XCTest, strict concurrency checks, generated-client diff, and the affected simulator and physical-device UI tests.

• Use sanitized fixtures and protected accounts only for final manual provider validation.

Dependencies

Post-1.0 work. Blocked until Mailflow 1.0.0 is released: https://github.com/Tutitoos/mailflow/milestone/9

Risks

Offline state, background execution, notification privacy, generated contracts, and device credentials can diverge from server truth. Use actors, Keychain, bounded caches, explicit conflict states, and real-device validation.

Out of scope

• Persistent cache, production authentication, mail screens, APNs, and TestFlight.