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/stores/focusTimer.svelte.ts

@@ -12,7 +12,7 @@
 // so closing the window mid-timer still gets you the "done" signal
 // on next launch.
 
-const STORAGE_KEY = "kon.focusTimer.v1";
+const STORAGE_KEY = "magnotia.focusTimer.v1";
 const TICK_INTERVAL_MS = 250;
 
 export type FocusTimerPersisted = {
@@ -114,7 +114,7 @@ function createFocusTimerStore() {
     writePersisted(null);
     stopTick();
     if (wasActive && typeof window !== "undefined") {
-      window.dispatchEvent(new CustomEvent("kon:focus-timer-cancelled"));
+      window.dispatchEvent(new CustomEvent("magnotia:focus-timer-cancelled"));
     }
   }
 
@@ -172,7 +172,7 @@ function createFocusTimerStore() {
       osc.onended = () => ctx.close().catch(() => {});
     } catch { /* audio is a nicety; never fatal */ }
 
-    window.dispatchEvent(new CustomEvent("kon:focus-timer-complete", {
+    window.dispatchEvent(new CustomEvent("magnotia:focus-timer-complete", {
       detail: { taskId, label },
     }));
   }