my-sea voice: persist the call across in-sea reloads via auto-rejoin; pngquant the RWS card back — TDD

Voice-persistence follow-up (user-spec item 6). Every my-sea navigation is a
full page reload that kills the WebSocket + peer connections; true no-reload
nav would need an SPA refactor of the heavily-tested draw IIFEs. Instead we
auto-rejoin: bindVoiceBtn remembers the active room in sessionStorage on join
and silently re-joins it on the next my-sea page if voice is still available
there (mic permission persists for the session, so no prompt). Same user-
visible result (a brief reconnect, not seamless) with no risk to the draw flows.

- burger-btn.js: sessionStorage 'mysea-voice-room' remember/forget helpers +
  window.mySeaVoiceForget; bindVoiceBtn refactored to startCall()/withVoiceRoom()
  and auto-rejoins on bind when the remembered room === the active btn's room.
  A failed join (e.g. INSECURE_CONTEXT) forgets the room so it doesn't retry.
- _my_sea_gear.html: the NVM-disconnect guard confirm + BYE forget the room
  (and leave the mesh) — an explicit leave shouldn't auto-rejoin.
- BurgerSpec: +4 auto-rejoin specs (match / different-sea / inactive / remember
  + forget). 438 Jasmine specs green.

Also (bundled, user's parallel work): pngquant the resaved RWS deck card back
(tarot-rider-waite-smith-back.png) from 733KB truecolor+a to a 264KB 8-bit
palette PNG, matching its companion card faces. Dimensions preserved (the
rotated 401x694).

Code architected by Disco DeDisco <discodedisco@outlook.com>
Git commit message Co-Authored-By:
Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/templates/apps/gameboard/_partials/_my_sea_gear.html

@@ -25,7 +25,11 @@ window.mySeaGuardedNav = window.mySeaGuardedNav || function (e, url) {
         window.showGuard(
             anchor,
             'Leave the Sea?<br>You’ll disconnect from voice.',
-            function () { window.location.href = url; },   // confirm
+            function () {                                   // confirm = leave
+                if (window.mySeaVoiceForget) window.mySeaVoiceForget();
+                if (window.VoiceRoom && window.VoiceRoom.leave) window.VoiceRoom.leave();
+                window.location.href = url;
+            },
             null,                                           // dismiss = stay
             { yesLabel: 'NVM' }
         );
@@ -42,7 +46,10 @@ window.mySeaGuardedNav = window.mySeaGuardedNav || function (e, url) {
     {% if leave_url %}
     <form method="POST" action="{{ leave_url }}" style="display:contents">
         {% csrf_token %}
-        <button type="submit" id="id_my_sea_bye_btn" class="btn btn-abandon">BYE</button>
+        {# BYE is an explicit leave — forget the room so the destination page #}
+        {# (and any return to my_sea) doesn't auto-rejoin the dropped call.   #}
+        <button type="submit" id="id_my_sea_bye_btn" class="btn btn-abandon"
+                onclick="if(window.mySeaVoiceForget)window.mySeaVoiceForget()">BYE</button>
     </form>
     {% endif %}
 </div>