skip login if not needed

downloader.py

@@ -66,6 +66,12 @@ def _goto_with_retry(context: BrowserContext, page: Page, url: str, retries: int
 def login(context: BrowserContext, page: Page) -> Page:
     logger.info("Logging in to Backblaze...")
     page = _goto_with_retry(context, page, f"{BASE_URL}/user_signin.htm")
+    if "user_signin" not in page.url:
+        logger.info("Already authenticated; skipping login form.")
+        return page
+    if page.locator("#email-field").count() == 0:
+        logger.info("Login form not present; assuming authenticated session.")
+        return page
     page.wait_for_selector("#email-field", timeout=30000)
     page.fill("#email-field", Config.BACKBLAZE_EMAIL)
     page.click("#submit-button")