fix(shopping): stale-row cleanup, cache-busting, view persistence

Root cause of the doubled lists: the relay DB had stale rows from
previous activations that were never deleted. The composite PK
prevented same-uid duplicates but not leftover rows from cards that
were deactivated without a successful DELETE.

Fixes:
  - Client tick sends DELETE { keep: [active uids] } after every
    push cycle. The relay drops all rows for this tenant that aren't
    in the keep list — cleans up migration leftovers, failed deletes,
    old single-list sentinels, everything in one shot.
  - Relay DELETE endpoint accepts { keep: [...] } for bulk cleanup
    alongside the existing { card_uid } single-delete.
  - Relay layout.php adds cache-busting query strings on style.css
    and app.js via filemtime() so phone browsers pick up new code
    on deploy instead of serving stale cached versions.
  - showView persists the active view name to localStorage; after
    login the relay restores it instead of always landing on compose.
  - Shopping-list-box border/background removed — items have their
    own chrome, the box is just a flex grouper now.
  - View title is always "Shopping"; each list box keeps its own
    header with the card title. No more doubled name.

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

relay/ui/layout.php

@@ -8,7 +8,7 @@ if (!defined('RELAY_BOOTSTRAPPED')) { http_response_code(404); exit; }
 <meta name="theme-color" content="#1e293b">
 <title>hyprcrd relay</title>
 <link rel="stylesheet" href="fonts/phosphor.css">
-<link rel="stylesheet" href="ui/style.css">
+<link rel="stylesheet" href="ui/style.css?v=<?= filemtime(__DIR__ . '/style.css') ?>">
 </head>
 <body>
 
@@ -263,6 +263,6 @@ if (!defined('RELAY_BOOTSTRAPPED')) { http_response_code(404); exit; }
 
 <div id="toast-stack"></div>
 
-<script src="ui/app.js"></script>
+<script src="ui/app.js?v=<?= filemtime(__DIR__ . '/app.js') ?>"></script>
 </body>
 </html>