Add a favicon and rework the Design page

Blogs had no icon at all, and browsers probing /favicon.ico ended up
rendering the 404 page. Ship a default paper & ink icon (svg + png) and
let each blog replace it from the Design page; /favicon.ico now serves
the default or redirects to the blog's own image. ICO uploads accepted.

The Design page gains colour schemes, reset to defaults, thumbnail
image pickers, jump links and a sticky save bar, plus new options:
heading font, link underline/hover, content box style and padding,
header image height, post dates and format, footer RSS toggle, menu
alignment/style/hover and sidebar width. The Menu card picks the
position with illustrated tiles and shows only the options that apply
to it, using CSS :checked rules rather than JavaScript.

All new defaults reproduce the previous look, so existing blogs are
unchanged until edited. Theme is jsonb, so no migration.

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

1 files changed, 21 insertions, 0 deletions

diff --git a/internal/web/handlers_media.go b/internal/web/handlers_media.go
index e651135..9d5a515 100644
--- a/internal/web/handlers_media.go
+++ b/internal/web/handlers_media.go
@@ -3,6 +3,7 @@ package web
 import (
 	"bytes"
 	"errors"
+	"io/fs"
 	"net/http"
 
 	"github.com/google/uuid"
@@ -36,3 +37,23 @@ func (s *Server) handleMedia(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("X-Content-Type-Options", "nosniff")
 	http.ServeContent(w, r, img.Filename, img.CreatedAt, bytes.NewReader(img.Data))
 }
+
+// handleFavicon answers the browsers that ask for /favicon.ico regardless of
+// the <link rel="icon"> tags: the blog's own icon if it set one, else the
+// Blogspace default. Without this the request would render the 404 page.
+func (s *Server) handleFavicon(w http.ResponseWriter, r *http.Request) {
+	if icon := ParseTheme(currentBlog(r).ThemeJSON).Favicon; icon != "" {
+		http.Redirect(w, r, "/media/"+icon, http.StatusFound)
+		return
+	}
+	data, err := fs.ReadFile(s.tpl.AssetsFS(), "favicon.png")
+	if err != nil {
+		s.serverError(w, err)
+		return
+	}
+	w.Header().Set("Content-Type", "image/png")
+	if !s.cfg.Dev {
+		w.Header().Set("Cache-Control", "public, max-age=3600")
+	}
+	w.Write(data)
+}