feat: 开源准备与 upgrade URL 构建时配置

- upgrade: SECRETS_UPGRADE_URL 改为构建时优先（option_env!），CI 自动注入
- upgrade: 支持运行时回退（.env/export），添加 dotenvy 加载 .env
- 泛化示例：IP/实例 ID/域名/密钥名改为示例值（10.0.0.1、example.com 等）
- tasks.json: 文件 secret 测试改用 test-fixtures/example-key.pem
- 文档更新：AGENTS.md、README.md

Made-with: Cursor

src/main.rs

@@ -7,6 +7,11 @@ mod models;
 mod output;
 
 use anyhow::Result;
+
+/// Load .env from current or parent directories (best-effort, no error if missing).
+fn load_dotenv() {
+    let _ = dotenvy::dotenv();
+}
 use clap::{Parser, Subcommand};
 use tracing_subscriber::EnvFilter;
 
@@ -76,25 +81,25 @@ EXAMPLES:
   # Add a server
   secrets add -n refining --kind server --name my-server \\
     --tag aliyun --tag shanghai \\
-    -m ip=47.117.131.22 -m desc=\"Aliyun Shanghai ECS\" \\
+    -m ip=10.0.0.1 -m desc=\"Example ECS\" \\
     -s username=root -s ssh_key=@./keys/server.pem
 
   # Add a service credential
   secrets add -n refining --kind service --name gitea \\
     --tag gitea \\
-    -m url=https://gitea.refining.dev -m default_org=refining \\
+    -m url=https://code.example.com -m default_org=myorg \\
     -s token=<token>
 
   # Add typed JSON metadata
   secrets add -n refining --kind service --name gitea \\
     -m port:=3000 \\
     -m enabled:=true \\
-    -m domains:='[\"gitea.refining.dev\",\"git.refining.dev\"]' \\
+    -m domains:='[\"code.example.com\",\"git.example.com\"]' \\
     -m tls:='{\"enabled\":true,\"redirect_http\":true}'
 
   # Add with token read from a file
   secrets add -n ricnsmart --kind service --name mqtt \\
-    -m host=mqtt.ricnsmart.com -m port=1883 \\
+    -m host=mqtt.example.com -m port=1883 \\
     -s password=@./mqtt_password.txt
 
   # Add typed JSON secrets
@@ -114,7 +119,7 @@ EXAMPLES:
         /// Kind of record: server, service, key, ...
         #[arg(long)]
         kind: String,
-        /// Human-readable unique name, e.g. gitea, i-uf63f2uookgs5uxmrdyc
+        /// Human-readable unique name, e.g. gitea, i-example0abcd1234efgh
         #[arg(long)]
         name: String,
         /// Tag for categorization (repeatable), e.g. --tag aliyun --tag hongkong
@@ -177,7 +182,7 @@ EXAMPLES:
         /// Filter by kind, e.g. server, service
         #[arg(long)]
         kind: Option<String>,
-        /// Exact name filter, e.g. gitea, i-uf63f2uookgs5uxmrdyc
+        /// Exact name filter, e.g. gitea, i-example0abcd1234efgh
         #[arg(long)]
         name: Option<String>,
         /// Filter by tag, e.g. --tag aliyun (repeatable for AND intersection)
@@ -423,8 +428,8 @@ EXAMPLES:
 
     /// Check for a newer version and update the binary in-place.
     ///
-    /// Downloads the latest release from Gitea and replaces the current binary.
-    /// No database connection or master key required.
+    /// Downloads the latest release and replaces the current binary. No database connection or master key required.
+    /// Release URL defaults to the upstream server; override via SECRETS_UPGRADE_URL for self-hosted or fork.
     #[command(after_help = "EXAMPLES:
   # Check for updates only (no download)
   secrets upgrade --check
@@ -530,6 +535,7 @@ enum ConfigAction {
 
 #[tokio::main]
 async fn main() -> Result<()> {
+    load_dotenv();
     let cli = Cli::parse();
 
     let filter = if cli.verbose {