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/preferences.svelte.ts

@@ -6,7 +6,7 @@ import type { AccessibilityPreferences, Preferences } from "$lib/types/app";
 import { errorMessage } from "$lib/utils/errors.js";
 import { toasts } from "./toasts.svelte.ts";
 
-export const PREFERENCES_CHANGED_EVENT = "kon:preferences-changed";
+export const PREFERENCES_CHANGED_EVENT = "magnotia:preferences-changed";
 
 type FontFamilies = Record<AccessibilityPreferences["fontFamily"], string>;