Show audio transcription fallback notice

[louis030195]

Summary

• expose the resolved audio transcription engine so saved Cloud/Deepgram settings can show when Whisper is actually active
• show a Recording settings alert with saved choice, active engine, and login/upgrade/use-Whisper actions
• send a /notify system notice when recording starts with Cloud or Deepgram falling back to local Whisper
• add resolver tests for Cloud login/subscription and Deepgram key fallback cases
• add an opt-in macOS WDIO e2e seed/spec for the Cloud -> Whisper fallback alert plus /notifications history

Test plan

• bun run typecheck
• bunx tsc --noEmit --target ES2022 --module ESNext --moduleResolution node --esModuleInterop --strict --skipLibCheck --types node,mocha,@wdio/globals/types e2e/specs/audio-fallback.spec.ts e2e/helpers/app-launcher.ts e2e/helpers/test-utils.ts e2e/helpers/screenshot-utils.ts
• cargo check --manifest-path apps/screenpipe-app-tauri/src-tauri/Cargo.toml
• cargo test --manifest-path apps/screenpipe-app-tauri/src-tauri/Cargo.toml --bin screenpipe-app screenpipe_cloud -- --nocapture
• cargo test --manifest-path apps/screenpipe-app-tauri/src-tauri/Cargo.toml --bin screenpipe-app deepgram_falls_back_without_api_key -- --nocapture

Not run: bun run test:e2e:audio-fallback:macos because this checkout needs a Tauri debug binary built with bun tauri build --no-sign --debug --verbose --no-bundle -- --features e2e first.

Note: cargo commands in this checkout rewrite the stale app entry in Cargo.lock, so I restored Cargo.lock after verification; the PR is intentionally scoped to the fallback UX.