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, 36 insertions, 9 deletions

diff --git a/internal/web/handlers_files.go b/internal/web/handlers_files.go
index 1d90b91..2b68871 100644
--- a/internal/web/handlers_files.go
+++ b/internal/web/handlers_files.go
@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"encoding/json"
 	"errors"
+	"html"
 	"io"
 	"mime/multipart"
 	"net/http"
@@ -12,6 +13,7 @@ import (
 	"strings"
 
 	"github.com/google/uuid"
+	"github.com/gramanas/blogspace/internal/markdown"
 	"github.com/gramanas/blogspace/internal/store"
 )
 
@@ -71,17 +73,42 @@ func fileMarkdown(f *store.File) string {
 	return open + text + "](/media/" + f.ID.String() + ")"
 }
 
-// appendFileMD is the no-JavaScript path of "Insert file": the file arrives
-// with the form itself and is appended to the end of the text on save.
-func appendFileMD(md string, f *store.File) string {
+// fileHTML is fileMarkdown for content written in HTML mode.
+func fileHTML(f *store.File) string {
+	name := html.EscapeString(f.Filename)
+	src := "/media/" + f.ID.String()
+	if f.Kind == "image" {
+		return `<img src="` + src + `" alt="` + name + `">`
+	}
+	return `<a href="` + src + `">` + name + `</a>`
+}
+
+// appendFile is the no-JavaScript path of "Insert file": the file arrives
+// with the form itself and is appended to the end of the text on save, in
+// the text's format.
+func appendFile(body string, f *store.File, format string) string {
 	if f == nil {
-		return md
+		return body
 	}
-	md = strings.TrimRight(md, "\n")
-	if md != "" {
-		md += "\n\n"
+	line := fileMarkdown(f)
+	if format == store.FormatHTML {
+		line = fileHTML(f)
+	}
+	body = strings.TrimRight(body, "\n")
+	if body != "" {
+		body += "\n\n"
+	}
+	return body + line + "\n"
+}
+
+// renderBody is what a save stores for the blog to show: Markdown is rendered
+// and sanitised, HTML goes out exactly as the blogger wrote it — the same
+// owner's decision as the custom HTML module (see AGENTS.md).
+func renderBody(format, src string) string {
+	if format == store.FormatHTML {
+		return src
 	}
-	return md + fileMarkdown(f) + "\n"
+	return markdown.Render(src)
 }
 
 // ---- file library ----------------------------------------------------------
@@ -182,7 +209,7 @@ func (s *Server) handleFileUpload(w http.ResponseWriter, r *http.Request) {
 			return
 		}
 		f := files[0]
-		writeJSON(w, http.StatusOK, map[string]any{"id": f.ID.String(), "filename": f.Filename, "kind": f.Kind, "size": f.Size, "markdown": fileMarkdown(f)})
+		writeJSON(w, http.StatusOK, map[string]any{"id": f.ID.String(), "filename": f.Filename, "kind": f.Kind, "size": f.Size, "markdown": fileMarkdown(f), "html": fileHTML(f)})
 		return
 	}
 	if msg != "" {