feat: Add initial project structure and dependencies

This commit introduces the foundational elements of the project:
- `.gitignore` file to exclude build artifacts and environment
  variables.
- `Cargo.lock` and `Cargo.toml` defining project dependencies and
  metadata.
- `diesel.toml` for Diesel CLI configuration.
- Initial migration files (`down.sql`, `up.sql`) for database schema
  setup.
- `rustfmt.toml` for code formatting.
- Basic module structure for database, routes, schema, state, and types.
- `src/main.rs` with basic Axum server setup and dotenv loading.
- `src/routes/system_router.rs` for basic API endpoint.
- `src/state.rs` for managing application state and database connection
  pool.
- Type definitions for Subsonic API responses and extensions.

src/routes/system_router.rs

@@ -0,0 +1,17 @@
+use crate::state::AppState;
+use crate::types::types::SubSonicResponses;
+use axum::{Json, Router, http::StatusCode, routing::get};
+
+pub fn system_routers() -> Router<AppState> {
+    Router::new().route(
+        "/getOpenSubsonicExtensions",
+        get(get_opensubsonic_extentions).post(get_opensubsonic_extentions),
+    )
+}
+
+async fn get_opensubsonic_extentions() -> (StatusCode, Json<SubSonicResponses>) {
+    (
+        StatusCode::OK,
+        Json(SubSonicResponses::open_subsonic_extentions()),
+    )
+}