Fix release v0.2.0 CI failures: CSC_NAME prefix + Linux deb maintainer (#5)

Two independent failures in the first v0.2.0 release run
(actions/runs/24572317217):

1. macOS signing refused the identity — electron-builder 26+ expects
   CSC_NAME to be the bare identity name without the
   "Developer ID Application: " prefix and chooses the certificate type
   automatically. Fixed by updating the repo secret out-of-band (stripped
   the prefix; no code change needed).

2. Linux .deb build failed with "Please specify author 'email' in the
   application package.json". Two fixes here so we stop getting bitten:

   - `package.json` — author expanded to object form with explicit
     `email: skiller@beautyfree.dev`. Satisfies electron-builder's default
     maintainer resolution.
   - `electron-builder.yml` — explicit `linux.maintainer` as a belt-and-
     suspenders fallback. If someone simplifies the author field back to
     a plain string later, the .deb target still builds cleanly.

Windows built successfully in the first run — that artifact path is
known good and doesn't need changes.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: beautyfree

electron-builder.yml

@@ -62,6 +62,10 @@ nsis:
 linux:
   icon: assets/icons/app/icon-512.png
   category: Development
+  # .deb requires a maintainer string. Mirrors package.json `author` but kept
+  # explicit so we don't get bitten again if someone simplifies the author
+  # field back to a plain string.
+  maintainer: "Skiller Contributors <skiller@beautyfree.dev>"
   target:
     - target: AppImage
       arch: [x64]

package.json

@@ -3,7 +3,10 @@
   "version": "0.2.0",
   "description": "A desktop app for managing AI agent skills across Claude Code, Cursor, Copilot, Gemini CLI, and more",
   "license": "MIT",
-  "author": "Skiller Contributors",
+  "author": {
+    "name": "Skiller Contributors",
+    "email": "skiller@beautyfree.dev"
+  },
   "repository": {
     "type": "git",
     "url": "https://github.com/beautyfree/skiller-skills-desktop-manager"