Add an HTML mode to posts, page intros and announcements

Markdown is the default and unchanged; the editor's new Format switch
stores the text as raw HTML instead, put on the blog exactly as written.
Like the custom HTML module it is unsanitised on purpose: the escape
hatch for embeds, scripts and inline styles that Markdown cannot express.

The source column keeps holding the text in both modes and a `format`
column says how to read it, so the public templates and the feed still
print the stored `*_html`. The dashboard preview of HTML goes into a
sandboxed iframe rather than the page, because a superadmin edits other
people's blogs and their markup must never run on the dashboard origin.
Search snippets of HTML posts are cut from a tag-stripped copy.

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

1 files changed, 16 insertions, 0 deletions

diff --git a/internal/store/store.go b/internal/store/store.go
index c8e97ea..30e5af0 100644
--- a/internal/store/store.go
+++ b/internal/store/store.go
@@ -18,6 +18,22 @@ import (
 var ErrNotFound = errors.New("not found")
 var ErrConflict = errors.New("already exists")
 
+// How a post, page intro or announcement source is read: Markdown (rendered
+// and sanitised) or raw HTML (put on the blog as written).
+const (
+	FormatMarkdown = "markdown"
+	FormatHTML     = "html"
+)
+
+// formatOrMD is what gets stored: an unset Format means Markdown, so callers
+// that predate the switch (the seed) keep working and the CHECK never fires.
+func formatOrMD(f string) string {
+	if f == FormatHTML {
+		return FormatHTML
+	}
+	return FormatMarkdown
+}
+
 type Store struct {
 	db      *pgxpool.Pool // control database
 	cluster *db.Cluster