refactor: separar SetAvatar en UploadMedia + SetAvatarURL

SetAvatar hacia dos cosas: subir la imagen y establecerla como avatar.
Ahora son tres funciones separadas:
- UploadMedia: solo sube, devuelve mxc:// URI
- SetAvatarURL: solo establece avatar con un mxc:// URI existente
- SetAvatar: convenience wrapper que llama a ambas

Permite subir imagenes sin activar el avatar, o reusar imagenes ya subidas.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

shell/matrix/profile.go

@@ -8,11 +8,13 @@ import (
 	"path/filepath"
 
 	"maunium.net/go/mautrix"
+	"maunium.net/go/mautrix/id"
 )
 
-// SetAvatar uploads the image at filePath to the Matrix media repository
-// and sets it as the bot's avatar. Returns the mxc:// URI of the upload.
-func (c *Client) SetAvatar(ctx context.Context, filePath string) (string, error) {
+// UploadMedia uploads the file at filePath to the Matrix media repository
+// and returns its mxc:// URI. Does NOT set the avatar — use SetAvatarURL
+// or SetAvatar for that.
+func (c *Client) UploadMedia(ctx context.Context, filePath string) (string, error) {
 	f, err := os.Open(filePath)
 	if err != nil {
 		return "", fmt.Errorf("open %s: %w", filePath, err)
@@ -39,13 +41,34 @@ func (c *Client) SetAvatar(ctx context.Context, filePath string) (string, error)
 		return "", fmt.Errorf("upload media: %w", err)
 	}
 
-	if err := c.raw.SetAvatarURL(ctx, resp.ContentURI); err != nil {
-		return "", fmt.Errorf("set avatar URL: %w", err)
-	}
-
 	return resp.ContentURI.String(), nil
 }
 
+// SetAvatarURL sets the bot's avatar to an already-uploaded mxc:// URI.
+func (c *Client) SetAvatarURL(ctx context.Context, mxcURI string) error {
+	parsed, err := id.ParseContentURI(mxcURI)
+	if err != nil {
+		return fmt.Errorf("parse mxc URI %q: %w", mxcURI, err)
+	}
+	if err := c.raw.SetAvatarURL(ctx, parsed); err != nil {
+		return fmt.Errorf("set avatar URL: %w", err)
+	}
+	return nil
+}
+
+// SetAvatar uploads the image at filePath and sets it as the bot's avatar.
+// Convenience wrapper: calls UploadMedia then SetAvatarURL.
+func (c *Client) SetAvatar(ctx context.Context, filePath string) (string, error) {
+	uri, err := c.UploadMedia(ctx, filePath)
+	if err != nil {
+		return "", err
+	}
+	if err := c.SetAvatarURL(ctx, uri); err != nil {
+		return "", err
+	}
+	return uri, nil
+}
+
 // SetDisplayName sets the bot's display name on the Matrix homeserver.
 func (c *Client) SetDisplayName(ctx context.Context, name string) error {
 	if err := c.raw.SetDisplayName(ctx, name); err != nil {