fix(hephaestus.x): refresh stale references in the "where it lives" spec

Fresh-browser test surfaced two staleness bugs on the standalone landing:

- Source link pointed at silentmode/silentmode — that repo was deleted last
  turn when we split into per-project repos. Point at silentmode/hephaestus
  now (which actually holds this landing page's home + the docker-compose /
  auth-proxy / Caddyfile that serves it).
- "Let's Encrypt TLS" was true for code.silentmode.st but not for hephaestus.x
  itself, which now uses a Silent Mode CA cert from Argonautica. Reword to
  reflect the dual-hostname primary/mirror architecture and the two cert
  stories.

Also mention the DR-backup relationship — the Sia bucket now mirrors the VPS
static content nightly, not the other way around.

hephaestus.x/index.html

@@ -82,10 +82,10 @@
 <section class="stack">
   <h2>Where it lives</h2>
   <dl class="spec">
-    <dt>forge</dt>       <dd><a href="https://code.silentmode.st/">code.silentmode.st</a> — Forgejo 10, Let's Encrypt TLS</dd>
-    <dt>this name</dt>   <dd><b>hephaestus.x</b> — on-chain BCNR certificate, chipnet, owner-controlled</dd>
-    <dt>storage</dt>     <dd>Sia network via <code>s3.silentmode.st:8600</code>, encrypted client-side</dd>
-    <dt>source</dt>      <dd><a href="https://code.silentmode.st/silentmode/silentmode">silentmode/silentmode</a> — under <code>Hephaestus/</code></dd>
+    <dt>forge</dt>       <dd><a href="https://code.silentmode.st/">code.silentmode.st</a> (mirror) · <b>hephaestus.x</b> (primary) — same Forgejo 10, dual-hostname</dd>
+    <dt>this name</dt>   <dd><b>hephaestus.x</b> — on-chain BCNR certificate, chipnet, owner-controlled, TLS via Silent Mode CA</dd>
+    <dt>storage</dt>     <dd>Sia network via <code>s3.silentmode.st:8600</code>, encrypted client-side · static landing mirrored to Sia bucket as DR backup</dd>
+    <dt>source</dt>      <dd><a href="https://code.silentmode.st/silentmode/hephaestus">silentmode/hephaestus</a> — the docker-compose + auth-proxy + Caddyfile</dd>
     <dt>protocol</dt>    <dd>BIP-137 "Bitcoin Signed Message" over BCH secp256k1 — any wallet that speaks Sign Message can log in</dd>
   </dl>
 </section>