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/lib/pages/FirstRunPage.svelte

@@ -225,9 +225,9 @@
   {:else if ritualsStep === "autostart"}
     <div class="w-full max-w-md mx-auto text-center">
       <Play size={32} strokeWidth={1.5} class="text-accent mx-auto mb-3" />
-      <h2 class="text-xl font-medium text-text">Launch Corbie at login?</h2>
+      <h2 class="text-xl font-medium text-text">Launch Magnotia at login?</h2>
       <p class="text-sm text-text-secondary mt-3 leading-relaxed">
-        So Corbie is already there when you need it — especially useful if you said yes to morning triage. Uses your OS's standard autostart. No background tricks, no telemetry.
+        So Magnotia is already there when you need it — especially useful if you said yes to morning triage. Uses your OS's standard autostart. No background tricks, no telemetry.
       </p>
       <p class="text-[11px] text-text-tertiary mt-3">You can change this any time in Settings.</p>
       <div class="flex items-center justify-center gap-3 mt-6">
@@ -270,7 +270,7 @@
 
   {:else}
     <div class="w-full">
-      <h2 class="text-2xl font-medium text-text text-center">Welcome to Kon</h2>
+      <h2 class="text-2xl font-medium text-text text-center">Welcome to Magnotia</h2>
       <p class="text-sm text-text-secondary text-center mt-2">Press the button. Start talking. That's it.</p>
 
       {#if error}