feat(gotify): Phase 3 C1 — Gotify REST API client

- src/gotify/api.rs: blocking reqwest 封装（§14）；health / applications
  / messages 三个方法；Bearer token 用 HeaderValue::set_sensitive
  标记，日志绝不泄露（§20）；10s per-request timeout
- src/gotify/model.rs: GotifyHealth / GotifyApplication / GotifyMessage
  DTO 镜像官方 wire schema；defaultPriority 加 rename（camelCase）
- src/gotify/mod.rs: re-export
- src/error.rs: 加 AppError::Gotify(String)
- Cargo.toml: reqwest 0.12 (blocking + json + rustls-tls) 从注释升级为真
  依赖（AGENTS.md §44 模板里早就列了，Phase 1 当时推迟）
- tests/gotify_api.rs: 6 个 JSON 解析测试

避坑：
- reqwest 0.12 默认 log Bearer token；要 set_sensitive(true) 才行
- reqwest::Error 转 AppError 不能用返回 impl Fn 的 helper（path 是
  &str 不是 'static）—— 改成每个调用点 inline closure
- Gotify 的 defaultPriority 是 camelCase，其他字段都是单字；
  用 #[serde(rename = "defaultPriority")] 单点 rename 而不是全局
  rename_all = "camelCase"（因为 Rust 端字段名是 snake_case）

验证：cargo build / build --release 都 exit 0，0 warning
- cargo test --test gotify_api: 6 passed; 0 failed
- debug   27.88 MB, subsystem = WINDOWS_CUI
- release  8.10 MB, subsystem = WINDOWS_GUI（reqwest 加进 release
  LTO 后体积几乎没变——rustls 是大头但被 strip + LTO 吃掉了）

tests/gotify_api.rs

@@ -0,0 +1,87 @@
+//! Gotify wire-format tests.
+//!
+//! Phase 3 V1 only validates JSON parsing — the actual HTTP layer is
+//! exercised manually against a real Gotify instance on the user's LAN.
+//! Adding `wiremock` / `httpmock` for in-process server mocking is a
+//! Phase 8 candidate once perf work makes a richer test suite useful.
+
+use windows_gotify_client_rust::gotify::model::{
+    GotifyApplication, GotifyHealth, GotifyMessage, ServerConfig,
+};
+
+#[test]
+fn server_config_trims_trailing_slash() {
+    let a = ServerConfig::new("https://gotify.example.com/", "tok");
+    assert_eq!(a.base_url, "https://gotify.example.com");
+    let b = ServerConfig::new("https://gotify.example.com", "tok");
+    assert_eq!(b.base_url, "https://gotify.example.com");
+}
+
+#[test]
+fn health_parses_green() {
+    let json = r#"{"health":"green","database":"sqlite"}"#;
+    let h: GotifyHealth = serde_json::from_str(json).unwrap();
+    assert_eq!(h.health, "green");
+    assert_eq!(h.database, "sqlite");
+}
+
+#[test]
+fn application_parses_minimal() {
+    let json = r#"{
+        "id": 1,
+        "name": "GitLab Runner",
+        "description": "CI build pings",
+        "defaultPriority": 1
+    }"#;
+    let app: GotifyApplication = serde_json::from_str(json).unwrap();
+    assert_eq!(app.id, 1);
+    assert_eq!(app.name, "GitLab Runner");
+    assert_eq!(app.default_priority, 1);
+}
+
+#[test]
+fn application_parses_with_optional_defaults() {
+    // Gotify may omit description / defaultPriority for clients created via
+    // a different code path. Make sure the `#[serde(default)]` works.
+    let json = r#"{ "id": 7, "name": "Airflow" }"#;
+    let app: GotifyApplication = serde_json::from_str(json).unwrap();
+    assert_eq!(app.id, 7);
+    assert_eq!(app.name, "Airflow");
+    assert_eq!(app.description, "");
+    assert_eq!(app.default_priority, 0);
+}
+
+#[test]
+fn message_parses_full_record() {
+    let json = r#"{
+        "id": 1024,
+        "appid": 1,
+        "message": "Deploy v1.4.2 to production completed in 3m 12s.",
+        "title": "Build succeeded",
+        "priority": 1,
+        "date": "2026-09-19T03:42:18.000Z",
+        "extras": {
+            "client::display": { "contentType": "text/markdown" }
+        }
+    }"#;
+    let msg: GotifyMessage = serde_json::from_str(json).unwrap();
+    assert_eq!(msg.id, 1024);
+    assert_eq!(msg.appid, 1);
+    assert_eq!(msg.priority, 1);
+    assert!(msg.extras.contains_key("client::display"));
+}
+
+#[test]
+fn message_parses_with_no_extras() {
+    let json = r#"{
+        "id": 99,
+        "appid": 2,
+        "message": "low battery",
+        "title": "",
+        "priority": 0,
+        "date": "2026-09-19T04:00:00Z"
+    }"#;
+    let msg: GotifyMessage = serde_json::from_str(json).unwrap();
+    assert_eq!(msg.title, "");
+    assert!(msg.extras.is_empty());
+}