Allow configuring environmental variables in panel (#626)

- [ ] Add test cases

src/ipc/utils/app_env_var_utils.ts

@@ -0,0 +1,71 @@
+/**
+ * DO NOT USE LOGGER HERE.
+ * Environment variables are sensitive and should not be logged.
+ */
+
+import { EnvVar } from "../ipc_types";
+
+// Helper function to parse .env.local file content
+export function parseEnvFile(content: string): EnvVar[] {
+  const envVars: EnvVar[] = [];
+  const lines = content.split("\n");
+
+  for (const line of lines) {
+    const trimmedLine = line.trim();
+
+    // Skip empty lines and comments
+    if (!trimmedLine || trimmedLine.startsWith("#")) {
+      continue;
+    }
+
+    // Parse key=value pairs
+    const equalIndex = trimmedLine.indexOf("=");
+    if (equalIndex > 0) {
+      const key = trimmedLine.substring(0, equalIndex).trim();
+      const value = trimmedLine.substring(equalIndex + 1).trim();
+
+      // Handle quoted values with potential inline comments
+      let cleanValue = value;
+      if (value.startsWith('"')) {
+        // Find the closing quote, handling escaped quotes
+        let endQuoteIndex = -1;
+        for (let i = 1; i < value.length; i++) {
+          if (value[i] === '"' && value[i - 1] !== "\\") {
+            endQuoteIndex = i;
+            break;
+          }
+        }
+        if (endQuoteIndex !== -1) {
+          cleanValue = value.slice(1, endQuoteIndex);
+          // Unescape escaped quotes
+          cleanValue = cleanValue.replace(/\\"/g, '"');
+        }
+      } else if (value.startsWith("'")) {
+        // Find the closing quote for single quotes
+        const endQuoteIndex = value.indexOf("'", 1);
+        if (endQuoteIndex !== -1) {
+          cleanValue = value.slice(1, endQuoteIndex);
+        }
+      }
+      // For unquoted values, keep everything as-is (including potential # symbols)
+
+      envVars.push({ key, value: cleanValue });
+    }
+  }
+
+  return envVars;
+}
+
+// Helper function to serialize environment variables to .env.local format
+export function serializeEnvFile(envVars: EnvVar[]): string {
+  return envVars
+    .map(({ key, value }) => {
+      // Add quotes if value contains spaces or special characters
+      const needsQuotes = /[\s#"'=&?]/.test(value);
+      const quotedValue = needsQuotes
+        ? `"${value.replace(/"/g, '\\"')}"`
+        : value;
+      return `${key}=${quotedValue}`;
+    })
+    .join("\n");
+}