feat(electron): add desktop application support with electron (#344)

* feat(electron): add desktop application support with electron

- implement complete Electron main process architecture with window management,
  app menu, IPC handlers, and settings window
- integrate Next.js server for production builds with embedded standalone server
- add configuration management with persistent storage and env file support
- create preload scripts with secure context bridge for renderer communication
- set up electron-builder configuration for multi-platform packaging (macOS,
  Windows, Linux)
- add GitHub Actions workflow for automated release builds
- include development scripts for hot-reload during Electron development

* feat(electron): enhance security and stability

- encrypt API keys using Electron safeStorage API before persisting to disk
- add error handling and rollback for preset switching failures
- extract inline styles to external CSS file and remove unsafe-inline from CSP
- implement dynamic port allocation with automatic fallback for production builds

* fix(electron): add maintainer field for Linux .deb package

- add maintainer email to linux configuration in electron-builder.yml
- required for building .deb packages

* fix(electron): use shx for cross-platform file copying

- replace Unix-only cp -r with npx shx cp -r
- add shx as devDependency for Windows compatibility

* fix(electron): fix runtime icon path for all platforms

- use icon.png directly instead of platform-specific formats
- electron-builder handles icon conversion during packaging
- macOS uses embedded icon from app bundle, no explicit path needed
- add icon.png to extraResources for Windows/Linux runtime access

* fix(electron): add security warning for plaintext API key storage

- warn user when safeStorage is unavailable (Linux without keyring)
- fail secure: throw error if encryption fails instead of storing plaintext
- prevent duplicate warnings with hasWarnedAboutPlaintext flag

* fix(electron): add remaining review fixes

- Add Windows ARM64 architecture support
- Add IPC input validation with config key whitelist
- Add server.js existence check before starting Next.js server
- Make afterPack throw error on missing directories
- Add workflow permissions for release job

---------

Co-authored-by: dayuan.jiang <jdy.toh@gmail.com>

scripts/prepare-electron-build.mjs

@@ -0,0 +1,41 @@
+#!/usr/bin/env node
+
+/**
+ * Prepare standalone directory for Electron packaging
+ * Copies the Next.js standalone output to a temp directory
+ * that electron-builder can properly include
+ */
+
+import { cpSync, rmSync, existsSync, mkdirSync } from "node:fs"
+import { join } from "node:path"
+import { fileURLToPath } from "node:url"
+
+const __dirname = fileURLToPath(new URL(".", import.meta.url))
+const rootDir = join(__dirname, "..")
+
+const standaloneDir = join(rootDir, ".next", "standalone")
+const staticDir = join(rootDir, ".next", "static")
+const targetDir = join(rootDir, "electron-standalone")
+
+console.log("Preparing Electron build...")
+
+// Clean target directory
+if (existsSync(targetDir)) {
+    console.log("Cleaning previous build...")
+    rmSync(targetDir, { recursive: true })
+}
+
+// Create target directory
+mkdirSync(targetDir, { recursive: true })
+
+// Copy standalone (includes node_modules)
+console.log("Copying standalone directory...")
+cpSync(standaloneDir, targetDir, { recursive: true })
+
+// Copy static files
+console.log("Copying static files...")
+const targetStaticDir = join(targetDir, ".next", "static")
+mkdirSync(targetStaticDir, { recursive: true })
+cpSync(staticDir, targetStaticDir, { recursive: true })
+
+console.log("Done! Files prepared in electron-standalone/")