feat: Add build scripts and runtime config support

Backend:
- Add setup-backend.sh/bat for one-click backend setup
- Fix test_auth.py mock settings (JWT_EXPIRE_HOURS)
- Fix test_excel_export.py TEMPLATE_DIR reference

Frontend:
- Add config.json for runtime API URL configuration
- Add init.js and settings.js for config loading
- Update main.js to load config from external file
- Update api.js to use dynamic API_BASE_URL
- Update all pages to initialize config before API calls
- Update package.json with extraResources for config

Build:
- Add build-client.sh/bat for packaging Electron + Sidecar
- Add build-all.ps1 PowerShell script with -ApiUrl parameter
- Add GitHub Actions workflow for Windows builds
- Add scripts/README.md documentation

This allows IT to configure backend URL without rebuilding.

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

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

client/package.json

@@ -29,19 +29,44 @@
     ],
     "extraResources": [
       {
-        "from": "../sidecar/dist",
-        "to": "sidecar",
+        "from": "../sidecar/dist/transcriber",
+        "to": "sidecar/transcriber",
         "filter": ["**/*"]
+      },
+      {
+        "from": "config.json",
+        "to": "config.json"
       }
     ],
     "win": {
-      "target": "portable"
+      "target": [
+        {
+          "target": "portable",
+          "arch": ["x64"]
+        }
+      ],
+      "icon": "assets/icon.ico"
     },
     "mac": {
-      "target": "dmg"
+      "target": [
+        {
+          "target": "dmg",
+          "arch": ["x64", "arm64"]
+        }
+      ],
+      "icon": "assets/icon.icns"
     },
     "linux": {
-      "target": "AppImage"
+      "target": [
+        {
+          "target": "AppImage",
+          "arch": ["x64"]
+        }
+      ],
+      "icon": "assets/icon.png"
+    },
+    "portable": {
+      "artifactName": "${productName}-${version}-portable.${ext}"
     }
   }
 }