fix(attachments): render inline cid: images in emails and feeds

Capture each attachment's Content-ID at ingestion (postal-mime and
mailparser paths) and rewrite cid: image refs to the stored /files URL
in processEmailContent, shared by the entry view and RSS/Atom feeds.
Bodyless HTML fragments are now serialized so sanitization and the cid
rewrite apply to them too.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/routes/entries.ts

@@ -140,7 +140,9 @@ export async function handle(c: Context<{ Bindings: Env }>): Promise<Response> {
             <dd>${new Date(emailData.receivedAt).toUTCString()}</dd>
           </dl>
           <div class="content">
-            ${raw(processEmailContent(emailData.content))}
+            ${raw(
+              processEmailContent(emailData.content, emailData.attachments),
+            )}
           </div>
           ${attachmentsSection}
         </body>