Add announcements: blog-wide notices on every page and post

A blog can have any number of announcements ("sections" in the schema):
a book club's next meeting, this month's pick, a holiday closure. Each
has a placement (above or below the posts, or under the menu when the
menu is a left sidebar), a look (highlighted, warning, plain), an order,
and an on/off switch so recurring notices can be kept around while hidden.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Sd8UPWrvyYCLj97JexNw3A

1 files changed, 23 insertions, 2 deletions

diff --git a/internal/web/handlers_blog.go b/internal/web/handlers_blog.go
index b768c4d..9b2fe5e 100644
--- a/internal/web/handlers_blog.go
+++ b/internal/web/handlers_blog.go
@@ -12,13 +12,17 @@ import (
 
 const postsPerPage = 10
 
-// blogView gathers what every public page needs: theme css, nav, the blog.
+// blogView gathers what every public page needs: theme css, nav, announcements, the blog.
 func (s *Server) blogView(r *http.Request) (map[string]any, error) {
 	blog := currentBlog(r)
 	pages, err := s.st.ListPages(r.Context(), blog.ID)
 	if err != nil {
 		return nil, err
 	}
+	sections, err := s.st.EnabledSections(r.Context(), blog.ID)
+	if err != nil {
+		return nil, err
+	}
 	theme := ParseTheme(blog.ThemeJSON)
 	var nav []store.Page
 	for _, p := range pages {
@@ -26,7 +30,24 @@ func (s *Server) blogView(r *http.Request) (map[string]any, error) {
 			nav = append(nav, p)
 		}
 	}
-	return map[string]any{"theme": theme, "css": theme.CSS(), "nav": nav}, nil
+	above, below, sidebar := splitSections(sections, theme.NavPosition == "left-sidebar")
+	return map[string]any{"theme": theme, "css": theme.CSS(), "nav": nav, "above": above, "below": below, "sidebar": sidebar}, nil
+}
+
+// splitSections groups announcements by placement. The sidebar only exists in
+// the left-sidebar layout; elsewhere sidebar announcements go above the content.
+func splitSections(secs []store.Section, hasSidebar bool) (above, below, sidebar []store.Section) {
+	for _, sec := range secs {
+		switch {
+		case sec.Placement == "below":
+			below = append(below, sec)
+		case sec.Placement == "sidebar" && hasSidebar:
+			sidebar = append(sidebar, sec)
+		default:
+			above = append(above, sec)
+		}
+	}
+	return
 }
 
 func (s *Server) handleBlogHome(w http.ResponseWriter, r *http.Request) {