Add --source CLI flag to override video source

src/main.cpp

@@ -100,6 +100,21 @@ int main(int argc, char* argv[]) {
     signal(SIGINT, signal_handler);
     signal(SIGTERM, signal_handler);
 
+    std::string cli_source;
+    for (int i = 2; i < argc; ++i) {
+        std::string a = argv[i];
+        if (a == "--source" || a == "-s") {
+            if (i + 1 < argc) {
+                cli_source = argv[++i];
+            } else {
+                std::cerr << "Error: --source requires a value" << std::endl;
+                return 1;
+            }
+        } else if (a.rfind("--source=", 0) == 0) {
+            cli_source = a.substr(9);
+        }
+    }
+
     if (argc < 2) {
         std::cout << "ByteTrack Counter (C++)" << std::endl;
         std::cout << "Version: " << version::GIT_COMMIT
@@ -109,13 +124,19 @@ int main(int argc, char* argv[]) {
         if (!version::GIT_TAG.empty())
             std::cout << " | tag: " << version::GIT_TAG;
         std::cout << std::endl;
-        std::cout << "Usage: bytetrack-counter <config.env>" << std::endl;
+        std::cout << "Usage: bytetrack-counter <config.env> [--source <rtsp://|http://|/path/to/file.mp4>]" << std::endl;
         std::cout << "  config.env  path to environment configuration file (required)" << std::endl;
+        std::cout << "  --source, -s  override video source (rtsp://, http://, or local file)" << std::endl;
         return 1;
     }
 
     g_config.load_from_env(argv[1]);
 
+    if (!cli_source.empty()) {
+        g_config.source = cli_source;
+        std::cout << "Source overridden by CLI: " << g_config.source << std::endl;
+    }
+
     std::cout << "Starting ByteTrack Counter (C++)" << std::endl;
     std::cout << "Version: " << version::GIT_COMMIT
               << " | branch: " << version::GIT_BRANCH