First start: create the config file and open the Config view

Without a config file arr-tui refused to start. It now creates an empty
one (private, with its directory) and opens the Config view. A service
with neither address nor key is "not configured", which validation
allows: its client returns ErrNotConfigured without a request, its
indicator stays grey, it is logged once as information, and its lists
say so instead of showing errors.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019reK4DUGYqDUjniWYJvwUW

internal/arr/image.go

@@ -135,6 +135,9 @@ func (e *notImageError) Error() string {
 // their URL base in image paths, so it must not be added twice.
 func (c *Client) resolve(ref string) (string, error) {
 	baseURL, _ := c.settings()
+	if baseURL == "" {
+		return "", ErrNotConfigured
+	}
 	base, err := url.Parse(baseURL)
 	if err != nil {
 		return "", err