Replace application.properties with config.properties:

- Renamed configuration file to `config.properties` for consistency.
- Updated `MediaManagerApplication` to load the new configuration file.
- Adjusted references in `README.md` and `.gitignore`.

src/main/java/com/mediamanager/MediaManagerApplication.java

@@ -40,9 +40,9 @@ public class MediaManagerApplication {
     private static void loadConfiguration() throws IOException {
         config = new Properties();
         try (InputStream input = MediaManagerApplication.class.getClassLoader()
-                .getResourceAsStream("application.properties")) {
+                .getResourceAsStream("config.properties")) {
             if (input == null) {
-                throw new IOException("Unable to find application.properties");
+                throw new IOException("Unable to find config.properties");
             }
             config.load(input);
             logger.info("Configuration loaded successfully");