feat(push): M7 Part 2 — opt-in push notifications (embedded ntfy distributor)

Implements the app side of M7 push (docs/android/PLAN.md §11). The app EMBEDS
its own distributor — ntfy is only the relay server, no second app installed,
no Google Play Services. New feature slice; no existing screen's data flow
changes.

- core/push: NtfyTopic (random unguessable topic + endpoint/SSE URL builders),
  PushTickle (content-free { stream, ref } parser over ntfy's SSE envelope),
  NtfyStreamClient (bare-client OkHttp SSE to <ntfy>/<topic>/sse, reconnect/
  backoff cloned from ShardStreamClient), PushNotifier (channels + per-stream
  deep-link notification), PushService (foreground service holding the
  connection), PushManager (mint topic / register-unregister device / start-stop,
  keyed to the session), PushPreferences (DataStore state).
- data: NotificationsApi + DTOs + NotificationsRepository over the merged
  /auth/me/devices + /auth/me/notifications/* contract; push block on SettingsDto.
- ui/notifications: settings screen + VM — per-stream toggles, personal streams
  greyed until a game account is linked, POST_NOTIFICATIONS request on enable.
- Navigation: Routes.NOTIFICATIONS + stream→route deep-link map, menu entry,
  RunicApp + MainActivity intent handling; teardown wired into logout + server
  switch (deregister while bearer valid) and every sign-out (local, via session
  observer).
- Manifest: POST_NOTIFICATIONS + FOREGROUND_SERVICE(_DATA_SYNC) + the service.

Deviation (recorded in PLAN.md): direct-ntfy transport, no UnifiedPush library
— the plan's stated likely path; keeps the APK Google-free and dependency-light,
with a PushResult/transport seam for a future FCM Play flavor. Requires the small
companion push.ntfyUrl settings field (website#<pr>).

18 new JVM tests; :app:testDebugUnitTest + lintDebug + assembleDebug green.

Co-Authored-By: Claude <noreply@anthropic.com>

app/src/main/res/values/strings.xml

@@ -257,4 +257,37 @@
     <string name="houses_empty">No houses are in danger right now.</string>
     <string name="houses_fallback_name">A house</string>
     <string name="houses_idoc_badge">IDOC</string>
+
+    <!-- ── Push notifications (§11, M7 Part 2) ─────────────────────────── -->
+    <string name="menu_notifications">Notifications</string>
+    <string name="notifications_title">Notifications</string>
+    <string name="notifications_subtitle">Choose what this shard notifies you about. Nothing is sent unless you turn it on.</string>
+    <string name="notifications_section_general">General</string>
+    <string name="notifications_section_personal">Your game account</string>
+    <string name="notifications_requires_link">Link a game account to enable this.</string>
+    <string name="notifications_empty">This shard offers no notification streams yet.</string>
+    <string name="notifications_unsupported">This shard hasn\'t set up push notifications yet.</string>
+    <string name="notifications_saved">Notification settings saved.</string>
+    <string name="notifications_all_off">Notifications turned off.</string>
+    <string name="notifications_save_error">Couldn\'t save your notification settings. Try again.</string>
+    <string name="notifications_relay_error">This shard\'s push relay isn\'t reachable right now.</string>
+
+    <!-- Notification channels + the ongoing foreground-service notification. -->
+    <string name="push_channel_messages">Shard notifications</string>
+    <string name="push_channel_messages_desc">Alerts you opted into from this shard.</string>
+    <string name="push_channel_service">Background connection</string>
+    <string name="push_channel_service_desc">Keeps the connection open to deliver notifications.</string>
+    <string name="push_service_title">Notifications active</string>
+    <string name="push_service_text">Listening for shard notifications.</string>
+
+    <!-- Per-stream notification titles (content-free tickle → generic title, §11). -->
+    <string name="push_stream_news_post">New post</string>
+    <string name="push_stream_server_status">Shard status changed</string>
+    <string name="push_stream_idoc_warning">A house is falling (IDOC)</string>
+    <string name="push_stream_champ_start">Champion spawn started</string>
+    <string name="push_stream_governor_election">New governor elected</string>
+    <string name="push_stream_vendor_sale">Your vendor made a sale</string>
+    <string name="push_stream_house_idoc">Your house entered IDOC</string>
+    <string name="push_stream_account_login">Login to your account</string>
+    <string name="push_stream_generic">New notification</string>
 </resources>