[codex] add Setapp macOS distribution flow

[seblavoie]

Summary

Adds a dedicated macOS Setapp distribution path for File Architect.

This introduces a separate Setapp build flavor, native Setapp entitlement bridge, Setapp-aware auth/updater/UI behavior, and a GitHub Actions job to build Setapp release artifacts without committing the Setapp SDK to the repo.

What Changed

• added a Setapp-specific Tauri config, Info.plist merge, build script, and native bridge
• added Setapp entitlement handling in the app auth flow
• disabled direct-sale updater and license UI behavior for Setapp builds
• added Setapp auth tests and technical spike / implementation docs
• added a separate GitHub Actions release job for Setapp macOS artifacts

Why

Setapp requires a separate macOS app flavor with its own bundle identifier, Setapp-managed activation, and no direct-sale licensing or updater flow in the shipped Setapp build.

Validation

• pnpm vitest run src/features/auth/__tests__/setappLicenseFlow.test.tsx
• cargo build --manifest-path src-tauri/Cargo.toml --bin filearchitect-app with VITE_IS_SETAPP=true
• scripts/build_setapp_macos.sh locally through compile, bundle, and signing

Remaining Note

Local notarization still depends on valid Apple notarization credentials. The Setapp build path itself now reaches that final notarization step.