feat: revamp drive management and activities UI

[OpenCow42]

Summary

• replace the crowded Setup list with Setup → Account → Drive navigation
• move File Provider, sync, Finder/Files, and macOS known-folder actions into dedicated drive management screens
• add per-drive action coordination, confirmations, stale-drive handling, animated navigation, and polished loading/error feedback
• replace the fixed Activities list with a stable, keyset-paginated timeline
• harden every Activities action with model-backed availability, duplicate guards, and visible failure feedback

Activities timeline

• load 50 mixed conflict and activity entries initially and prefetch older pages near the end
• preserve the visible event while older pages append or live database updates arrive
• provide day grouping, compact expandable rows, paging retry states, end-of-history feedback, and Back to Latest
• resolve File Provider item URLs only after the user selects Open in Finder or Open in Files
• query errors and related-conflict exclusions in SQLite with composite and partial indexes
• keep clear and full support-log export semantics independent of UI pagination
• add a deterministic 1,000-event UI fixture and scroll performance coverage

Activities action reliability

• keep dismissible action errors visible above loaded, empty, initial-error, and unavailable-database states
• disable Refresh, Clear, Export, and filtering only when their model operations cannot run, with matching internal guards against rapid or programmatic calls
• make destructive Clear exclusive with loading, Refresh, and Export while allowing the read-only Refresh and Export operations to overlap
• reset the reader to the newest event only after Clear succeeds
• report unavailable domains/items and rejected Files presentations through an injectable item-opening boundary
• preserve Finder reveal/select behavior and moved/deleted feedback on macOS
• report clipboard write failures inline and show Copied only after a successful platform write
• preserve child action accessibility identifiers when timeline rows expand

CI and UI-test reliability

• support the macOS SwiftUI tab representation, which exposes app tabs as radio buttons rather than tab-bar buttons
• make text assertions work with both accessibility labels and macOS accessibility values
• use stable timeline-entry identifiers for pagination and Back to Latest checks
• make the unavailable-database fixture deterministic instead of falling back to the production event store
• provide a labeled Setup error-dismissal control with a native Escape shortcut on macOS

Validation

• all six macOS UI tests that previously failed in CI pass locally when run individually
• the unchanged UI cases passed in the initial local macOS suite
• the exact unsigned macOS CI build passed
• iOS Simulator and visionOS Simulator test bundles compiled successfully
• focused Activities unit suite passed on iOS Simulator 26.5
• focused Activities unit suite passed on visionOS Simulator 26.5
• focused Activities unit cases passed on macOS, including Finder-specific behavior
• macOS app build passed
• generic visionOS build passed
• git diff --check passed
• a combined local macOS UI rerun encountered an Xcode LaunchServices worker relaunch stall between tests; this was separate from assertions, and each repaired case passed in an isolated run

Documentation

• update app/domain, conflicts, persistence, and logging documentation for the new navigation, timeline behavior, and action reliability semantics