Add initial project structure with configuration, printing, and routing functionality

- Created a new Rust project with Cargo configuration.
- Added `.gitignore` to exclude target directory.
- Implemented `Cargo.lock` for dependency management.
- Defined application configuration in `config/app.yaml` and `src/config.rs`.
- Developed printing logic in `src/printer.rs` using `cups_rs` for printer interactions.
- Established routing and request handling in `src/routes.rs` for health checks and print requests.
- Introduced a scheduler in `src/scheduler.rs` to manage print job distribution.
- Created models for print parameters and job responses in `src/models.rs`.
- Set up the main application entry point in `src/main.rs` with server initialization and configuration loading.
- Included necessary dependencies in `Cargo.toml` for async handling, tracing, and configuration management.

config/app.yaml

@@ -0,0 +1,28 @@
+server:
+  bind: "0.0.0.0"
+  port: 8080
+
+cups:
+  server: "http://v4.hitwh.games:631"
+  user: "root"
+  password: "lanyimin123"
+# 如需指定 CUPS 服务器/用户，示例：
+# cups:
+#   server: "http://cups.local:631"
+#   user: "printsvc"
+
+scheduler:
+  strategy: "least_queued" # round_robin | least_queued
+  refresh_interval_secs: 10
+
+retry:
+  attempts: 3
+  backoff_ms: 1500
+
+defaults:
+  copies: 1
+  duplex: "two_sided_long_edge" # one_sided | two_sided_long_edge | two_sided_short_edge
+  color: "auto"                # auto | color | monochrome
+  media: "A4"
+  quality: "normal"            # draft | normal | high
+