Add native self-hosted instance connection to fluxer_desktop

Trimmed monorepo checkout (fluxer_desktop + packages/voice_engine_v2 +
tools/ci) with a "Connect to a Different Server" menu item and popout
that lets the desktop app switch to any self-hosted Fluxer instance,
plus fixes for well-known discovery on single-domain self-hosted
deployments and a false-positive ERR_ABORTED on same-origin client
redirects during the switch. Defaults to chat.fluxr.chat and uses an
isolated userData directory from the official build.

fluxer_desktop/native/system-hunspell/index.d.ts

@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+export interface SystemDictionary {
+	tag: string;
+	affPath: string;
+	dicPath: string;
+}
+
+export declare class Hunspell {
+	constructor(affPath: string, dicPath: string);
+
+	spell(word: string): boolean;
+
+	suggest(word: string, max?: number): Array<string>;
+
+	add(word: string): void;
+
+	remove(word: string): void;
+
+	close(): void;
+}
+
+export declare function discoverSystemDictionaries(): Array<SystemDictionary>;
+
+export declare function hashFile(path: string): Promise<string>;
+
+export declare const loadError: Error | null;