Implement native Android PebbleBridge

[caco3]

This PR introduces a native Android bridge (PebbleBridge) that lets watchapp config pages running in the mobile app’s WebView access capabilities that are normally blocked by WebView sandboxing, CORS, mixed-content rules, or JavaScript restrictions. See #301 for details.

When a watchapp declares the config_network_bridge capability, its config page receives a window.pebbleBridge object that delegates work to the native side. This allows a config page to:

• Fetch from any HTTP/HTTPS endpoint (window.pebbleBridge.fetch) — including local or self-hosted services that would otherwise be unreachable from a mobile WebView.
• Open WebSocket connections (window.pebbleBridge.WebSocket) — for streaming live data without WebSocket CORS issues.
• Persist small amounts of data securely (window.pebbleBridge.storage) — using the app’s encrypted storage instead of localStorage, which is not shared across sessions or reliable in a WebView.
• Close the config page and return data to the watchapp (window.pebbleBridge.close) — replacing the legacy pebblejs://close# URL scheme.

The bridge is opt-in per watchapp and only activates when the app declares the config_network_bridge capability, so existing watchapps are unaffected.

Example use cases

• A Home Assistant client config page that queries the HA REST API and WebSocket directly, populates an entity picker, and returns selected entities to the watchapp — all without requiring the watchapp itself to proxy the data. Effectively this is the purpose of h this PR. I am working on extending https://github.com/skylord123/pebble-home-assistant-ws for this (see Load entities through android bridge caco3/pebble-home-assistant-ws#4)
• A weather watchapp that fetches forecast data from a provider API and lets the user pick a location or unit system before returning the choice to the watch.

For easy testing, I created a minimal demo watchapp, see https://github.com/caco3/bridge-demo. It demonstrates internet access through the config page.

Key changes

• Added NetworkBridge (config_network_bridge) capability detection in LockerAppScreen and PebbleRoutes.
• Added a bridgeEnabled flag to WatchappSettingsRoute and passed it into WatchappSettingsScreen.
• Implemented PebbleBridgeManager, which registers PebbleBridgeNativeInterface on the WebView and injects a JS shim that creates window.pebbleBridge.
• Implemented native bridge APIs:
  • fetch(url, options) — HTTP via Ktor/OkHttp
  • WebSocket(url, protocols) — WebSocket via Ktor with message/close/error forwarding
  • storage.get/set/remove — Android EncryptedSharedPreferences
  • close(returnValue) — closes the config page and returns data to the app
• Added BridgeConfigParser to read config values from the URL hash fragment.
• Added BridgeModels, BridgeFetch, BridgeStorage, and BridgeWebSocket modules.
• Updated the iOS webViewFactory signature for source compatibility (no iOS implementation yet).

Backward compatibility

Apps that do not declare config_network_bridge see no change.

Documentation

See coredevices/sdk-docs#17

High-level architecture

┌──────────────────────────────────────────────┐
│  Watch app config page (HTML/JS)             │
│  window.pebbleBridge.fetch(...)              │
│  window.pebbleBridge.WebSocket(...)          │
│  window.pebbleBridge.storage.get/set(...)    │
└──────────────────────────────────────────────┘
                       │
                       ▼
┌──────────────────────────────────────────────┐
│  JS shim (assets/bridge-shim.js)             │
│  Creates Promise-based API from native       │
└──────────────────────────────────────────────┘
                       │
                       ▼
┌──────────────────────────────────────────────┐
│  PebbleBridgeManager (Android)               │
│  - Shared Ktor/OkHttp HttpClient             │
│  - BridgeFetch, BridgeWebSocket              │
│  - BridgeStorage (EncryptedSharedPreferences)│
│  - PebbleBridgeNativeInterface (@JS)         │
└──────────────────────────────────────────────┘
                       │
      ┌────────────────┼────────────────┐
      ▼                ▼                ▼
  Ktor/OkHttp     Ktor/OkHttp     EncryptedShared
  fetch           WebSocket         Preferences

Notes

• iOS support is intentionally out of scope; the iOS factory signature was updated only to keep the project compiling. I don't have access to iOS thus am unable to implement and test it for iOS.
• No public API changes outside the Pebble module.
• The code was generated using AI. My Kotlin skills are very limited, but I reviewed it am confident that it is ok.

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