Add .env.example with default configuration

Author: ihmily

.env.example

@@ -0,0 +1,9 @@
+# StreamCap runtime environment configuration
+# PLATFORM: Runtime platform for the application, supports 'desktop' or 'web' modes (default: desktop)
+PLATFORM=desktop
+
+# HOST: Web server host address (default: 127.0.0.1, used for local development)
+HOST=127.0.0.1
+
+# PORT: Web server port number (default: 6006)
+PORT=6006