Fix 500 errors and double-slash URLs found during sexp rendering testing

- events: fix ImportError for events_url (was importing from shared.utils
  instead of shared.infrastructure.urls)
- blog: add missing ~mobile-filter sexp component (details/summary panel)
- shared: fix double-slash URLs in ~auth-menu, ~cart-mini, ~header-row
  by removing redundant "/" concatenation on URLs that already have trailing slash
- blog: fix ghost_sync select UnboundLocalError caused by redundant local
  import shadowing module-level import

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

shared/sexp/tests/test_components.py

@@ -21,7 +21,7 @@ class TestCartMini:
     def test_empty_cart_shows_logo(self):
         html = sexp(
             '(~cart-mini :cart-count cart-count :blog-url blog-url :cart-url cart-url)',
-            **{"cart-count": 0, "blog-url": "https://blog.example.com", "cart-url": "https://cart.example.com"},
+            **{"cart-count": 0, "blog-url": "https://blog.example.com/", "cart-url": "https://cart.example.com/"},
         )
         assert 'id="cart-mini"' in html
         assert "logo.jpg" in html
@@ -31,7 +31,7 @@ class TestCartMini:
     def test_nonempty_cart_shows_badge(self):
         html = sexp(
             '(~cart-mini :cart-count cart-count :blog-url blog-url :cart-url cart-url)',
-            **{"cart-count": 3, "blog-url": "https://blog.example.com", "cart-url": "https://cart.example.com"},
+            **{"cart-count": 3, "blog-url": "https://blog.example.com/", "cart-url": "https://cart.example.com/"},
         )
         assert 'id="cart-mini"' in html
         assert "fa-shopping-cart" in html
@@ -60,7 +60,7 @@ class TestAuthMenu:
     def test_logged_in(self):
         html = sexp(
             '(~auth-menu :user-email user-email :account-url account-url)',
-            **{"user-email": "alice@example.com", "account-url": "https://account.example.com"},
+            **{"user-email": "alice@example.com", "account-url": "https://account.example.com/"},
         )
         assert 'id="auth-menu-desktop"' in html
         assert 'id="auth-menu-mobile"' in html
@@ -71,7 +71,7 @@ class TestAuthMenu:
     def test_logged_out(self):
         html = sexp(
             '(~auth-menu :account-url account-url)',
-            **{"account-url": "https://account.example.com"},
+            **{"account-url": "https://account.example.com/"},
         )
         assert "fa-solid fa-key" in html
         assert "sign in or register" in html