feat(artist): resolve patreon + subscribestar display names at add-time (#130 step 5)

Parity with pixiv (operator ask): the extension add now resolves the real
display name for our other native platforms too, not just the URL handle.
patreon_resolver.resolve_display_name reads the campaigns API's
attributes.name; SubscribeStarClient.resolve_display_name pulls the creator
name off the profile page (og:title, else the <title> stripped of the
SubscribeStar suffix). extension_service._resolve_artist_name dispatches per
platform (pixiv=token, patreon/subscribestar=cookies via get_cookies_path),
best-effort in an executor, falling back to the readable URL handle on any
failure. Still all curator core — the extension is unchanged (sends only the
URL). gallery-dl platforms keep the handle (readable, no native client).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CDgx8bQS5YrGRK76v8HUnM

backend/app/services/subscribestar_client.py

@@ -273,6 +273,30 @@ def _parse_ss_datetime(text: str) -> str | None:
     return None
 
 
+_OG_TITLE_RE = re.compile(
+    r'<meta[^>]+property=["\']og:title["\'][^>]+content=["\']([^"\']+)["\']',
+    re.IGNORECASE,
+)
+_TITLE_RE = re.compile(r"<title[^>]*>(.*?)</title>", re.IGNORECASE | re.DOTALL)
+# Trailing " | SubscribeStar" / " on SubscribeStar" the profile <title> carries.
+_SS_TITLE_SUFFIX_RE = re.compile(
+    r"\s*[|·]\s*SubscribeStar.*$|\s+on\s+SubscribeStar.*$", re.IGNORECASE
+)
+
+
+def _extract_creator_name(html: str) -> str | None:
+    """The creator's display name from a SubscribeStar profile page: prefer the
+    og:title meta (it's the bare creator name), else the <title> with the
+    SubscribeStar suffix stripped. None when neither yields anything (#130)."""
+    m = _OG_TITLE_RE.search(html)
+    name = unescape(m.group(1)).strip() if m else ""
+    if not name:
+        t = _TITLE_RE.search(html)
+        raw = unescape(t.group(1)).strip() if t else ""
+        name = _SS_TITLE_SUFFIX_RE.sub("", raw).strip()
+    return name or None
+
+
 class SubscribeStarClient:
     """Synchronous SubscribeStar HTML-scrape read client. Construct with a path
     to a Netscape cookies.txt (the same file CredentialService.get_cookies_path
@@ -604,6 +628,23 @@ class SubscribeStarClient:
             current = next_href
             first_page = False
 
+    # -- display name -------------------------------------------------------
+
+    def resolve_display_name(self, campaign_id: str) -> str | None:
+        """The creator's display name from their profile page, used to name the
+        Artist at add-time (#130). `campaign_id` is the creator URL. None on any
+        failure — the caller falls back to the URL handle. Sync: run in an
+        executor."""
+        base, slug = _split_creator_url(campaign_id)
+        if not slug:
+            return None
+        self._session.headers["Referer"] = f"{base}/"
+        try:
+            html = self._feed_html(f"{base}/{slug}")
+        except SubscribeStarAPIError:
+            return None
+        return _extract_creator_name(html)
+
     # -- verify ------------------------------------------------------------
 
     def verify_auth(self, campaign_id: str) -> tuple[bool | None, str]: