Add mobile app, map-core, nearby sync, and activity recording specs

mobile-app: Unified React Native + Expo app combining Planner and
Journal. OAuth2 PKCE auth, MapLibre maps, versioned REST API with
Zod schemas, configurable server URL, offline SQLite, Web Push relay
notifications. TanStack Query + Zustand state management. Jest +
Maestro testing. 76 tasks across 5 phases.

map-core-package: Extract renderer-agnostic map definitions (tiles,
color palettes, POI categories, z-index) into @trails-cool/map-core.
Pure refactor preparing for MapLibre on mobile. 27 tasks.

mobile-activity-recording: GPS recording, live stats, HealthKit/Health
Connect export. Separated from mobile-app for independent scheduling.

mobile-nearby-sync: BLE route sync between nearby devices for offline
group riding. QR waypoint sharing as simpler v1. TXQR noted as future.

journal-rest-api spec: Full API contract — endpoints, auth, pagination,
errors, discovery, versioning, BRouter proxy.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

openspec/changes/mobile-app/specs/shared-packages/spec.md

@@ -0,0 +1,30 @@
+## MODIFIED Requirements
+
+### Requirement: React Native compatibility for types package
+The `@trails-cool/types` package SHALL work in React Native without modification.
+
+#### Scenario: Types import in mobile app
+- **WHEN** the mobile app imports interfaces from `@trails-cool/types`
+- **THEN** all types resolve correctly with no DOM or Node.js API dependencies
+
+### Requirement: React Native compatibility for gpx package
+The `@trails-cool/gpx` package SHALL work in React Native by using a platform-appropriate XML parser.
+
+#### Scenario: GPX parsing on mobile
+- **WHEN** the mobile app calls `parseGpx()` with a GPX string
+- **THEN** the package uses the React Native runtime's DOMParser (or a polyfill) instead of `linkedom`, and returns the same typed output as on Node.js
+
+#### Scenario: GPX generation on mobile
+- **WHEN** the mobile app calls `generateGpx()` with route data
+- **THEN** the package produces valid GPX XML without relying on Node.js APIs
+
+### Requirement: React Native compatibility for i18n package
+The `@trails-cool/i18n` package SHALL work in React Native with the same translation files.
+
+#### Scenario: i18n initialization on mobile
+- **WHEN** the mobile app initializes i18n using `@trails-cool/i18n`
+- **THEN** translations load correctly and `useTranslation()` works in React Native components
+
+#### Scenario: Language switching
+- **WHEN** the user changes language in the mobile app's Profile tab
+- **THEN** all strings update to the selected language using the shared translation files