fix(desktop): unblock Windows + Linux release packaging

Two unrelated bugs were preventing the GitHub-hosted runner desktop
release matrix from succeeding:

1. Windows job failed with `spawnSync electron-vite ENOENT`. On
   Windows the package-local binaries are `.cmd` shims and Node's
   `spawnSync` does not consult PATHEXT unless going through a shell.
   Pass `shell: true` for both the electron-vite and electron-builder
   spawns; on POSIX hosts these are real executables so the shell hop
   is harmless.

2. Linux `.deb`/`.rpm` job failed with electron-builder errors:
   `Please specify project homepage` and `Please specify author
   'email'`. fpm requires a maintainer when generating .deb, and
   electron-builder derives it from the app package.json metadata. Add
   `description`, `homepage`, `repository`, `author` (with
   email) and `license` to apps/desktop/package.json so the Linux
   targets have the metadata they need.

Refs: https://nodejs.org/api/child_process.html#spawning-bat-and-cmd-files-on-windows
Refs: https://www.electron.build/configuration.html#metadata

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

apps/desktop/package.json

@@ -2,6 +2,18 @@
   "name": "@multica/desktop",
   "version": "0.1.0",
   "private": true,
+  "description": "Multica Desktop — native desktop client for the Multica platform.",
+  "homepage": "https://multica.ai",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/multica-ai/multica.git",
+    "directory": "apps/desktop"
+  },
+  "author": {
+    "name": "Multica",
+    "email": "support@multica.ai"
+  },
+  "license": "UNLICENSED",
   "main": "./out/main/index.js",
   "scripts": {
     "bundle-cli": "node scripts/bundle-cli.mjs",

apps/desktop/scripts/package.mjs

@@ -329,10 +329,18 @@ function main() {
   //
   // CI invokes this script via `node scripts/package.mjs`, so we cannot
   // rely on pnpm/npm to inject package-local binaries into PATH.
+  //
+  // `shell: true` is required on Windows: `node_modules/.bin/electron-vite`
+  // ships as a `.cmd` shim there, and Node's `spawnSync` does not honour
+  // PATHEXT when spawning a bare command without a shell — it would fail
+  // with `ENOENT`. On POSIX hosts the shim is a real executable so going
+  // through the shell is harmless. See
+  // https://nodejs.org/api/child_process.html#spawning-bat-and-cmd-files-on-windows
   const viteResult = spawnSync("electron-vite", ["build"], {
     stdio: "inherit",
     cwd: desktopRoot,
     env: envWithLocalBins(),
+    shell: true,
   });
   if (viteResult.error) {
     console.error(
@@ -391,10 +399,13 @@ function main() {
     });
 
     // Step 4: invoke electron-builder for the current target only.
+    // `shell: true` for the same Windows `.cmd` shim reason as the
+    // electron-vite invocation above.
     const result = spawnSync("electron-builder", builderArgs, {
       stdio: "inherit",
       cwd: desktopRoot,
       env: envWithLocalBins(),
+      shell: true,
     });
 
     if (result.error) {