feat: add markets and payments management pages

- New markets blueprint at /<slug>/markets/ with create/delete
- New payments blueprint at /<slug>/payments/ with SumUp config
- Register both in events app with context processor for markets
- Remove PageConfig feature flag check from calendar creation
  (feature toggles replaced by direct management pages)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

bp/calendars/services/calendars.py

@@ -5,7 +5,6 @@ from sqlalchemy.ext.asyncio import AsyncSession
 
 from models.calendars import Calendar
 from models.ghost_content import Post  # for FK existence checks
-from models.page_config import PageConfig
 import unicodedata
 import re
 
@@ -88,12 +87,6 @@ async def create_calendar(sess: AsyncSession, post_id: int, name: str) -> Calend
     if not post.is_page:
         raise CalendarError("Calendars can only be created on pages, not posts.")
 
-    pc = (await sess.execute(
-        select(PageConfig).where(PageConfig.post_id == post_id)
-    )).scalar_one_or_none()
-    if pc is None or not (pc.features or {}).get("calendar"):
-        raise CalendarError("Calendar feature is not enabled for this page. Enable it in page settings first.")
-
     # Look for existing (including soft-deleted)
     q = await sess.execute(
         select(Calendar).where(Calendar.post_id == post_id, Calendar.name == name)