feat(config): persist database URL to ~/.config/secrets/config.toml

- Add 'secrets config set-db/show/path' subcommands
- Remove dotenvy and DATABASE_URL env var support
- Config file created with 0600 permission
- Bump version to 0.3.0

Made-with: Cursor

src/config.rs

@@ -0,0 +1,70 @@
+use anyhow::{Context, Result};
+use serde::{Deserialize, Serialize};
+use std::fs;
+use std::path::PathBuf;
+
+#[derive(Debug, Serialize, Deserialize, Default)]
+pub struct Config {
+    pub database_url: Option<String>,
+}
+
+pub fn config_dir() -> PathBuf {
+    dirs::config_dir()
+        .unwrap_or_else(|| PathBuf::from("~/.config"))
+        .join("secrets")
+}
+
+pub fn config_path() -> PathBuf {
+    config_dir().join("config.toml")
+}
+
+pub fn load_config() -> Result<Config> {
+    let path = config_path();
+    if !path.exists() {
+        return Ok(Config::default());
+    }
+    let content = fs::read_to_string(&path)
+        .with_context(|| format!("读取配置文件失败: {}", path.display()))?;
+    let config: Config = toml::from_str(&content)
+        .with_context(|| format!("解析配置文件失败: {}", path.display()))?;
+    Ok(config)
+}
+
+pub fn save_config(config: &Config) -> Result<()> {
+    let dir = config_dir();
+    fs::create_dir_all(&dir).with_context(|| format!("创建配置目录失败: {}", dir.display()))?;
+
+    let path = config_path();
+    let content = toml::to_string_pretty(config).context("序列化配置失败")?;
+    fs::write(&path, &content).with_context(|| format!("写入配置文件失败: {}", path.display()))?;
+
+    // 设置文件权限为 0600（仅所有者读写）
+    #[cfg(unix)]
+    {
+        use std::os::unix::fs::PermissionsExt;
+        let perms = fs::Permissions::from_mode(0o600);
+        fs::set_permissions(&path, perms)
+            .with_context(|| format!("设置文件权限失败: {}", path.display()))?;
+    }
+
+    Ok(())
+}
+
+/// 按优先级解析数据库连接串：
+/// 1. --db-url CLI 参数（非空时使用）
+/// 2. ~/.config/secrets/config.toml 中的 database_url
+/// 3. 报错并提示用户配置
+pub fn resolve_db_url(cli_db_url: &str) -> Result<String> {
+    if !cli_db_url.is_empty() {
+        return Ok(cli_db_url.to_string());
+    }
+
+    let config = load_config()?;
+    if let Some(url) = config.database_url
+        && !url.is_empty()
+    {
+        return Ok(url);
+    }
+
+    anyhow::bail!("数据库未配置。请先运行：\n\n    secrets config set-db <DATABASE_URL>\n")
+}