chore: rebrand from Kon/Corbie to Magnotia

Replace all instances of the legacy product names "Kon" and "Corbie" with
"Magnotia" across user-facing copy, code identifiers, package names, bundle
ids, file paths, and documentation. Preserves the unrelated "konsole" (KDE
terminal) reference and the parent CORBEL company name.

- Renames 10 Rust crates (kon-* → magnotia-*) and the tauri binary
- Updates package.json, tauri.conf.json (productName + identifier)
- Renames CSS classes (kon-rh-* → magnotia-rh-*) and animations
- Renames brand and roadmap docs
- Regenerates Cargo.lock and package-lock.json

Verified: svelte-check passes; pure-rust crates compile under new names.

src/routes/+page.svelte

@@ -14,7 +14,7 @@
   });
 </script>
 
-<main class="h-full overflow-hidden" aria-label="Kon application content">
+<main class="h-full overflow-hidden" aria-label="Magnotia application content">
   {#if page.current === "first-run"}
     <FirstRunPage />
   {:else if page.current === "dictation"}