scp81: fix RAM LOAD block splitting (overlapping 1-byte shifts) (v2.1.12)

The block slicer used the block number as a character offset
(loadfile_tlv[i * 2:(i + 240) * 2]), so every LOAD block after the first was
a 1-byte-shifted copy of the previous one - the cap header repeated every
239 bytes on the wire. A live install accepted three blocks, failed block 4
with SW 6400, then 6985, and INSTALL [for install] answered 6A88. The same
slicing was inherited by the SCP81 helper from the SCP80 path, so
multi-block caps could not install there either; both are fixed.

Tests: blocks are consecutive and reassemble the C4 TLV byte-for-byte
(200 python); findings updated; service worker v149.

frontend/index.html

@@ -18,7 +18,7 @@
 <div class="max-w-7xl mx-auto px-6 py-2">
 
 	<div class="flex items-center justify-between mb-3">
-		<h1 class="text-2xl font-bold text-heading">OTAMan <span id="slogan" class="text-sm font-normal text-gray-500 dark:text-slate-400 ml-2" data-l10n="SIM OTA with a Human Face">SIM OTA with a Human Face</span> <span class="text-xs text-gray-400 dark:text-slate-500 ml-1">v2.1.11</span></h1>
+		<h1 class="text-2xl font-bold text-heading">OTAMan <span id="slogan" class="text-sm font-normal text-gray-500 dark:text-slate-400 ml-2" data-l10n="SIM OTA with a Human Face">SIM OTA with a Human Face</span> <span class="text-xs text-gray-400 dark:text-slate-500 ml-1">v2.1.12</span></h1>
 		<div class="flex items-center gap-4">
 			<span id="state-indicator" class="flex items-center select-none" style="cursor:default" title="Connecting...">
 				<span id="state-indicator-dot" class="text-xs text-gray-400" title="Connecting...">●</span>

frontend/sw.js

@@ -1,4 +1,4 @@
-const CACHE = 'otaman-v148';
+const CACHE = 'otaman-v149';
 const URLS = [
   'index.html',
   'help.html',