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

Cargo.toml

@@ -1,13 +1,13 @@
 [package]
 name = "secrets"
-version = "0.2.0"
+version = "0.3.0"
 edition = "2024"
 
 [dependencies]
 anyhow = "1.0.102"
 chrono = { version = "0.4.44", features = ["serde"] }
 clap = { version = "4.6.0", features = ["derive", "env"] }
-dotenvy = "0.15.7"
+dirs = "6.0.0"
 serde = { version = "1.0.228", features = ["derive"] }
 serde_json = "1.0.149"
 sqlx = { version = "0.8.6", features = ["runtime-tokio", "tls-rustls", "postgres", "uuid", "json", "chrono"] }