Consolidate Sentry config into shared package; fix inconsistencies

Introduces @trails-cool/sentry-config with three helpers that encode
the common Sentry.init options:
- nodeSentryConfig(appContext) for the two HTTP servers
- browserSentryConfig(appContext, env) for the Journal client
- mobileSentryConfig(__DEV__) for the React Native app
- drop404s beforeSend for servers

Also fixes three inconsistencies found in the audit:
- Planner server was missing sendDefaultPii: false (IPs could leak)
- Planner entry.server.tsx didn't call Sentry.captureException on SSR
  render errors; Journal's SSR did
- Sentry.init location now matches across apps (both in server.ts;
  Journal previously had it in app/entry.server.tsx, which meant init
  ran lazily on first request rather than at server startup)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/mobile/package.json

@@ -38,6 +38,7 @@
     "@trails-cool/gpx": "workspace:*",
     "@trails-cool/i18n": "workspace:*",
     "@trails-cool/map-core": "workspace:*",
+    "@trails-cool/sentry-config": "workspace:*",
     "@trails-cool/types": "workspace:*",
     "expo": "~55.0.15",
     "expo-constants": "~55.0.14",