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>

electron/main/env-loader.ts

@@ -0,0 +1,67 @@
+import fs from "node:fs"
+import path from "node:path"
+import { app } from "electron"
+
+/**
+ * Load environment variables from .env file
+ * Searches multiple locations in priority order
+ */
+export function loadEnvFile(): void {
+    const possiblePaths = [
+        // Next to the executable (for portable installations)
+        path.join(path.dirname(app.getPath("exe")), ".env"),
+        // User data directory (persists across updates)
+        path.join(app.getPath("userData"), ".env"),
+        // Development: project root
+        path.join(app.getAppPath(), ".env.local"),
+        path.join(app.getAppPath(), ".env"),
+    ]
+
+    for (const envPath of possiblePaths) {
+        if (fs.existsSync(envPath)) {
+            console.log(`Loading environment from: ${envPath}`)
+            loadEnvFromFile(envPath)
+            return
+        }
+    }
+
+    console.log("No .env file found, using system environment variables")
+}
+
+/**
+ * Parse and load environment variables from a file
+ */
+function loadEnvFromFile(filePath: string): void {
+    try {
+        const content = fs.readFileSync(filePath, "utf-8")
+        const lines = content.split("\n")
+
+        for (const line of lines) {
+            const trimmed = line.trim()
+
+            // Skip comments and empty lines
+            if (!trimmed || trimmed.startsWith("#")) continue
+
+            const equalIndex = trimmed.indexOf("=")
+            if (equalIndex === -1) continue
+
+            const key = trimmed.slice(0, equalIndex).trim()
+            let value = trimmed.slice(equalIndex + 1).trim()
+
+            // Remove surrounding quotes
+            if (
+                (value.startsWith('"') && value.endsWith('"')) ||
+                (value.startsWith("'") && value.endsWith("'"))
+            ) {
+                value = value.slice(1, -1)
+            }
+
+            // Don't override existing environment variables
+            if (!(key in process.env)) {
+                process.env[key] = value
+            }
+        }
+    } catch (error) {
+        console.error(`Failed to load env file ${filePath}:`, error)
+    }
+}