cli: avoid data-dir initialization for version; create db parent dirs; redact generated passwords in CLI output

- Prevent 'nx9-wg version' from creating data directories by avoiding database initialization.
- Create parent directories when an explicit --database path is provided.
- Redact printed generated administrator passwords; announce file path or redact instead.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

crates/nx9-wg-db/src/error.rs

@@ -0,0 +1,44 @@
+//! Database error types.
+
+use thiserror::Error;
+
+/// Result type for database operations.
+pub type Result<T> = std::result::Result<T, DbError>;
+
+/// Database-specific errors.
+#[derive(Debug, Error)]
+pub enum DbError {
+    /// Entity was not found.
+    #[error("entity not found: {0}")]
+    NotFound(String),
+
+    /// Unique or foreign key constraint violation.
+    #[error("constraint violation: {0}")]
+    ConstraintViolation(String),
+
+    /// Conflict, e.g. entity already exists.
+    #[error("conflict: {0}")]
+    Conflict(String),
+
+    /// Validation error when converting from raw database values.
+    #[error("validation error: {0}")]
+    Validation(String),
+
+    /// SQLx database error.
+    #[error("database error: {0}")]
+    Sqlx(#[from] sqlx::Error),
+
+    /// Migration failure.
+    #[error("migration error: {0}")]
+    Migration(String),
+
+    /// Internal or unexpected error.
+    #[error("internal database error: {0}")]
+    Internal(String),
+}
+
+impl From<nx9_wg_core::error::Nx9Error> for DbError {
+    fn from(err: nx9_wg_core::error::Nx9Error) -> Self {
+        Self::Validation(err.to_string())
+    }
+}