fix(extension): show Add-to-FC button on subscribed Patreon creators (#1485)

Symptom (operator-flagged): the extension injected the Add-as-source button on
a Patreon creator you had NOT subscribed to, but it disappeared once you were
subscribed — the opposite of when it's useful.

Root cause (extension logic, not Patreon security): Patreon serves a creator
under three URL shapes — bare patreon.com/Atole, patreon.com/c/Atole, and
patreon.com/cw/Atole (the 'creator workspace' URL you land on once subscribed;
documented in patreon_resolver._VANITY_RE). The button's artist-page gate
(PLATFORM_ARTIST_PATTERNS.patreon in platforms.js) and its byte-mirror probe
pattern (_PLATFORM_PATTERNS in extension_service._derive) only matched the bare
single-segment form and explicitly excluded c/. So the subscribed-view URL
failed the gate → no button. The ingestion resolver already handled all three;
only these two gates were too narrow.

Fix: both regexes now accept optional cw/ and c/ prefixes and drop the strict
single-segment end-anchor, so a creator's inner page (/cw/Atole/posts,
/Atole/membership) also matches — robust to whatever exact shape the subscribed
view uses. Nav-page exclusions (home/search/messages/notifications/library/
settings/posts + post permalinks) preserved. New unit test covers all three
prefixes, sub-paths, and nav-page rejection (both regexes validated identically).

Bump extension 1.0.7→1.0.8 so a fresh signed XPI ships the fix (also exercises
batch-5 web-ext-10's AMO sign path end-to-end on the main build).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/app/services/extension_service.py

@@ -35,9 +35,14 @@ class InvalidUrlError(Exception):
 # reviewers catch drift.
 _PLATFORM_PATTERNS: list[tuple[str, re.Pattern[str]]] = [
     ("patreon", re.compile(
+        # Three creator URL shapes — bare (patreon.com/Atole), `c/`, and `cw/`
+        # (the "creator workspace" URL served once subscribed, see
+        # patreon_resolver._VANITY_RE). A trailing sub-path is allowed so a
+        # creator's inner page still derives the slug. Nav pages stay excluded.
         r"^https?://(?:www\.)?patreon\.com/"
-        r"(?!home$|search\b|messages\b|notifications\b|library\b|settings\b|posts\b|c/)"
-        r"(?P<slug>[^/?#]+)/?$",
+        r"(?:cw/|c/)?"
+        r"(?!(?:home|search|messages|notifications|library|settings|posts)(?:[/?#]|$))"
+        r"(?P<slug>[^/?#]+)",
         re.IGNORECASE,
     )),
     ("subscribestar", re.compile(