rename: the apps say Inkwell — web, desktop, Android and server strings

ThoughtSync is renamed Inkwell ("Fabled Inkwell" in full; Scribe note 5071).
This is step 1 of milestone 481: every string a person reads in the running
apps. Identities installed clients depend on are deliberately untouched — the
Tauri productName (it derives the .deb Package: field), identifier and binary
name, applicationId, X-ThoughtSync-* headers, the export's app marker, env vars,
module and crate names.

- web: title, PWA manifest (name "Fabled Inkwell", short_name "Inkwell"),
  offline page, icon labels, build labels, prompts, notification title
- server: site_name default, import error, link-preview User-Agent
- 0030: a stored site_name of exactly the old default follows the rename. The
  Settings page saves every key, so most servers hold "ThoughtSync" without an
  admin ever having chosen it; a name they typed is left alone
- desktop: window title, default device name, local-mode site name, log line
- android: app_name and the strings that name the app
- core: probe and compatibility messages

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/public/offline.html

@@ -4,7 +4,7 @@
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <meta name="theme-color" content="#F5C518" />
-    <title>Offline · ThoughtSync</title>
+    <title>Offline · Inkwell</title>
     <style>
       :root {
         color-scheme: light dark;
@@ -107,7 +107,7 @@
         </g>
       </svg>
       <h1>You're offline</h1>
-      <p>ThoughtSync needs a connection to your server to load. Reconnect and try again.</p>
+      <p>Inkwell needs a connection to your server to load. Reconnect and try again.</p>
       <button type="button" onclick="location.reload()">Retry</button>
     </main>
   </body>