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/viewer/+layout@.svelte

@@ -32,7 +32,7 @@
   // Sync settings from main window
   if (typeof window !== "undefined") {
     window.addEventListener("storage", (e) => {
-      if (e.key === "kon_settings" && e.newValue) {
+      if (e.key === "magnotia_settings" && e.newValue) {
         try { Object.assign(settings, JSON.parse(e.newValue)); } catch {}
       }
     });

src/routes/viewer/+page.svelte

@@ -92,8 +92,8 @@
   }
 
   onMount(() => {
-    loadFromHandoff(localStorage.getItem("kon_viewer_item"));
-    const mode = localStorage.getItem("kon_viewer_mode");
+    loadFromHandoff(localStorage.getItem("magnotia_viewer_item"));
+    const mode = localStorage.getItem("magnotia_viewer_mode");
     if (mode === "edit" || mode === "view") viewerMode = mode;
 
     // Listen for new items via storage events
@@ -139,7 +139,7 @@
   }
 
   function handleStorageChange(e: StorageEvent) {
-    if (e.key === "kon_viewer_item" && e.newValue) {
+    if (e.key === "magnotia_viewer_item" && e.newValue) {
       void loadFromHandoff(e.newValue);
     }
   }
@@ -317,7 +317,7 @@
     if (!item) return;
     try {
       localStorage.setItem(
-        "kon_viewer_item",
+        "magnotia_viewer_item",
         JSON.stringify({ id: String(item.id), stamp: Date.now() }),
       );
     } catch {}
@@ -391,7 +391,7 @@
     onpointerdown={handleDragStart}
   >
     <span class="text-[12px] font-medium text-text-secondary tracking-wide">
-      Kon - {viewerMode === "edit" ? "Editor" : "Viewer"}
+      Magnotia - {viewerMode === "edit" ? "Editor" : "Viewer"}
     </span>
     <div class="flex-1"></div>
   </div>