feat: implement filament and spool preset services with CRUD operations

- Add `FilamentService` for managing filament inventory, including creation, retrieval, updating, and deletion of filaments.
- Introduce `SpoolPresetService` for handling spool presets, allowing users to create, update, and delete their custom presets.
- Create domain models for `Filament` and `SpoolPreset` with necessary fields and methods.
- Define repository interfaces for filament and spool preset persistence.
- Implement application configuration management from environment variables.
- Set up error handling with a centralized `AppError` type.
- Build the Axum router with public and protected routes for user authentication and resource management.

backend/src/main.rs

@@ -0,0 +1,43 @@
+use dotenvy::dotenv;
+use sqlx::postgres::PgPoolOptions;
+use std::net::SocketAddr;
+use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt, EnvFilter};
+
+mod adapters;
+mod application;
+mod config;
+mod domain;
+mod error;
+mod ports;
+mod router;
+
+#[tokio::main]
+async fn main() -> anyhow::Result<()> {
+    dotenv().ok();
+
+    tracing_subscriber::registry()
+        .with(EnvFilter::try_from_default_env().unwrap_or_else(|_| "meowspool=debug,tower_http=debug".into()))
+        .with(tracing_subscriber::fmt::layer())
+        .init();
+
+    let config = config::Config::from_env()?;
+
+    tracing::info!("Connecting to database...");
+    let db_pool = PgPoolOptions::new()
+        .max_connections(10)
+        .connect(&config.database_url)
+        .await?;
+
+    tracing::info!("Running migrations...");
+    sqlx::migrate!("./migrations").run(&db_pool).await?;
+
+    let app = router::build(db_pool, config.clone());
+
+    let addr: SocketAddr = format!("{}:{}", config.host, config.port).parse()?;
+    tracing::info!("Server listening on {}", addr);
+
+    let listener = tokio::net::TcpListener::bind(addr).await?;
+    axum::serve(listener, app).await?;
+
+    Ok(())
+}