Release v1.0.3 - Add zip file creation to release process

- Update /release command to create zip files in releases/ folder
- Add v1.0.3 zip files for both Chrome and Firefox extensions

Files modified:
- .claude/commands/release.md
- releases/plebeian-signer-chrome-v1.0.3.zip (new)
- releases/plebeian-signer-firefox-v1.0.3.zip (new)

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

package.json

@@ -1,12 +1,12 @@
 {
   "name": "plebeian-signer",
-  "version": "v1.0.2",
+  "version": "v1.0.3",
   "custom": {
     "chrome": {
-      "version": "v1.0.2"
+      "version": "v1.0.3"
     },
     "firefox": {
-      "version": "v1.0.2"
+      "version": "v1.0.3"
     }
   },
   "scripts": {