fix #221: scale image pastes, drop text box, fix raw view and size

- image pastes render the image scaled to fit the viewer box (aspect
  ratio preserved, max-height 70vh), no text/code box below it
- link pill moved under the image as a small inline chip
- /raw serves image attachment bytes as an image instead of empty text
- view details size reports the actual attachment file size

internal/web/templates/paste.html

@@ -39,19 +39,27 @@
   {{if .Attachment}}
   <div class="float">
     <div class="attachment-bar">
+      {{if .AttachmentImage}}
+      <div class="attachment-preview"><img src="/f/{{.Attachment.ID}}/{{.Attachment.Filename}}" alt="{{.Attachment.Filename}}"></div>
+      <a class="attachment-chip" href="/f/{{.Attachment.ID}}/{{.Attachment.Filename}}" data-mime="{{.Attachment.Mime}}">
+        <span class="attachment-name">{{.Attachment.Filename}}</span>
+        <span class="attachment-size">{{.Attachment.SizeHuman}}</span>
+      </a>
+      {{else}}
       <a class="attachment-chip" href="/f/{{.Attachment.ID}}/{{.Attachment.Filename}}" data-mime="{{.Attachment.Mime}}">
         <span class="attachment-name">{{.Attachment.Filename}}</span>
         <span class="attachment-size">{{.Attachment.SizeHuman}}</span>
       </a>
-      {{if or (eq .Attachment.Mime "image/png") (eq .Attachment.Mime "image/jpeg") (eq .Attachment.Mime "image/gif") (eq .Attachment.Mime "image/webp")}}
       <div class="attachment-preview"><img src="/f/{{.Attachment.ID}}/{{.Attachment.Filename}}" alt="{{.Attachment.Filename}}"></div>
       {{end}}
     </div>
   </div>
   {{end}}
+  {{if not .AttachmentImage}}
   <div class="float">
     <div class="code" id="code"><div class="gutter" id="gutter">{{.Gutter}}</div><div class="codebody" id="codebody">{{.ContentHTML}}</div></div>
   </div>
+  {{end}}
 </div>
 <input type="hidden" id="raw-content" value="{{.ContentAttr}}">
 <script src="/static/paste.js" defer data-paste-id="{{.ID}}"></script>