Move calendar management to /{slug}/admin/ and reserve slug

- Change calendars blueprint prefix from /calendars to /admin
- Simplify routes from /calendars/ to / within blueprint
- Reserve admin, markets, payments, entries as calendar slugs
- Update blog admin nav link to /{slug}/admin/

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

events/app.py

@@ -90,8 +90,8 @@ def create_app() -> "Quart":
         url_prefix="/<slug>",
     )
 
-    # Calendars nested under post slug: /<slug>/<calendar_slug>/...
-    # Listing stays at /<slug>/calendars/, individual at /<slug>/<calendar_slug>/
+    # Calendar admin under post slug: /<slug>/admin/
+    # Individual calendars at /<slug>/<calendar_slug>/
     app.register_blueprint(
         register_calendars(),
         url_prefix="/<slug>",

events/bp/calendars/routes.py

@@ -21,7 +21,7 @@ from shared.browser.app.utils.htmx import is_htmx_request
 
 
 def register():
-    bp = Blueprint("calendars", __name__, url_prefix='/calendars')
+    bp = Blueprint("calendars", __name__, url_prefix='/admin')
     bp.register_blueprint(
       register_calendar(),
     )
@@ -32,7 +32,7 @@ def register():
 
     # ---------- Pages ----------
 
-    @bp.get("/calendars/")
+    @bp.get("/")
     @cache_page(tag="calendars")
     async def home(**kwargs):
         from shared.sexp.page import get_template_context
@@ -46,7 +46,7 @@ def register():
         return await make_response(html)
 
 
-    @bp.post("/calendars/new/")
+    @bp.post("/new/")
     @require_admin
     @clear_cache(tag="calendars", tag_scope="all")
     async def create_calendar(**kwargs):

events/bp/calendars/services/calendars.py

@@ -86,7 +86,9 @@ async def create_calendar(sess: AsyncSession, post_id: int, name: str) -> Calend
     name = (name or "").strip()
     if not name:
         raise CalendarError("Calendar name must not be empty.")
-    slug=slugify(name)
+    slug = slugify(name)
+    if slug in ("admin", "markets", "payments", "entries"):
+        raise CalendarError(f'"{slug}" is a reserved name and cannot be used as a calendar name.')
 
     # Ensure post exists (avoid silent FK errors in some DBs)
     raw = await fetch_data("blog", "post-by-id", params={"id": post_id}, required=False)