Add Apple on-device (FoundationModels) coach provider + rich notifications

[hoveeman]

Adds an "On-device (Apple)" provider that runs the AI coach entirely on the device via FoundationModels — no API key, no network, fully private. It falls back to a chosen cloud provider (OpenAI/Gemini/OpenRouter) when the local model is unavailable or a generation fails.

Give this a try as I was having some issues with PRs. let me know if i need to take another look.

Provider:

• AppleFoundationModelsClient: a ResponsesClient adapter (one-shot, tool-less in v1) using FoundationModels guided generation for structured cards, with a text/JSON fallback. Mirrors the GeminiClient request-body translation.
• AppleOnDeviceAvailability: friendly wrapper over SystemLanguageModel availability; guarded with #if canImport(FoundationModels) / @available so the project still compiles on older SDKs.
• FallbackResponsesClient + CoachClientResolver: unify provider resolution across chat/summaries/notifications and add the on-device → cloud-backup chain.
• Settings: On-device provider option, cloud-backup picker, privacy card.

Notifications (leveraging free/private local inference):

• Richer check-ins: actionable tip + tappable follow-up + adaptive skip.
• New midday slot alongside morning/evening.
• Proactive anomaly alerts (low SpO2, short sleep), event-driven and on-device-only, deduped per kind per day.
• On-device check-ins use a BGProcessingTask (longer budget, no network required); cloud providers keep BGAppRefreshTask. Adds the com.pulseloop.coach.process background-task identifier.
• Fixes a latent crash: background scheduling now gates on actual BGTask registration (the host app could otherwise submit an unregistered identifier under XCTest).

How was this tested?

Tested on my iPhone 17 Pro Max

[hoveeman]

Some screenshots:

[saksham2001]

This is really cool! What iOS version did you test this on @hoveeman? Did you have to update to iOS 27?

[hoveeman]

This is really cool! What iOS version did you test this on @hoveeman? Did you have to update to iOS 27?

i am on 26.5.1

My son has his phone on iOS 27. I'll try and get it loaded on his as well.

[saksham2001]

This is a great feature, thank you @hoveeman! I tested the PR and I love the on-device model - some of the replies seem better than bigger models. The tool calls also work well.

I made some minor changes to not fallback to other models (so we can clearly see the error and user can switch manually to a model that works). Also made some configurations changes like removing the input image feature as that is not available for the on-device model yet.

[hoveeman]

This is a great feature, thank you @hoveeman! I tested the PR and I love the on-device model - some of the replies seem better than bigger models. The tool calls also work well.

I made some minor changes to not fallback to other models (so we can clearly see the error and user can switch manually to a model that works). Also made some configurations changes like removing the input image feature as that is not available for the on-device model yet.

That's great! Glad you enjoyed it! There may be an opportunity to add a fallback model in the future for certain types of prompts that may not work properly with the on device model. However for now, that's a good idea to remove it!