feat(electron): bundle draw.io for offline support (#629)

* feat(electron): bundle draw.io for offline support

- Download draw.io static files during CI build (v29.3.5)
- Detect Electron and use local draw.io files instead of CDN
- Add offline=1 parameter to disable external service calls
- Skip /drawio path from i18n middleware redirect
- Add public/drawio/ to .gitignore (downloaded during build)

This allows the Electron app to work completely offline.

* chore: bump version to 0.4.12-beta.3 for offline test

* fix(electron): ad-hoc sign macOS app for bundled draw.io compatibility

* chore: bump version to 0.4.12-beta.4 for ad-hoc sign test

* fix(electron): disable electron-builder signing to use custom ad-hoc signing

* chore: bump version to 0.4.12-beta.5

scripts/afterPack.cjs

@@ -1,6 +1,7 @@
 /**
  * electron-builder afterPack hook
  * Copies node_modules to the standalone directory in the packaged app
+ * and ad-hoc signs macOS apps for offline draw.io bundle compatibility
  */
 
 const {
@@ -12,6 +13,7 @@ const {
     statSync,
 } = require("fs")
 const path = require("path")
+const { execSync } = require("child_process")
 
 /**
  * Copy directory recursively, converting symlinks to regular files/directories.
@@ -80,4 +82,22 @@ module.exports = async (context) => {
                 "Ensure 'npm run electron:prepare' was run before building.",
         )
     }
+
+    // Ad-hoc sign macOS apps to fix signature issues with bundled draw.io files
+    if (context.packager.platform.name === "mac") {
+        const appPath = path.join(
+            appOutDir,
+            `${context.packager.appInfo.productFilename}.app`,
+        )
+        console.log(`[afterPack] Ad-hoc signing macOS app: ${appPath}`)
+        try {
+            execSync(`codesign --force --deep --sign - "${appPath}"`, {
+                stdio: "inherit",
+            })
+            console.log("[afterPack] Ad-hoc signing completed successfully")
+        } catch (error) {
+            console.error("[afterPack] Ad-hoc signing failed:", error.message)
+            throw error
+        }
+    }
 }