Port 4ducky to Rust (Axum + SQLite)

Same design, layout, URLs and features as the PHP version: browse grid,
image view with AJAX comments, BBCode, likes, uploads (file, URL and
bookmarklet), quicktagger, profile, block list, inbox, invites, Hall of
Ducks, Truhe, abuse reports and the admin tools.

- Parameterized SQL, escaped templates (askama), argon2 passwords,
  server-side sessions, CSRF tokens on every write, strict script CSP
- SSRF-safe remote image fetching, magic-byte upload checks
- Self-hosted captcha replaces reCAPTCHA v1; analytics/social widgets removed
- Vanilla JS replaces jQuery and its plugins with the same DOM behaviour
- Reverse proxy support (frontend_path, trust_proxy, secure_cookies)
- Admin CLI: admin, settings, invites

See README.md for running it and the full list of changes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

templates/ajax/upload.html

@@ -0,0 +1,39 @@
+{%- if !errors.is_empty() %}
+
+    <ul>
+    {%- for e in errors %}
+ 		<li>{{ e|safe }}</li>
+    {%- endfor %}
+    </ul>
+
+{%- else %}
+
+  <form id="UForm"  action="/upload" method="post" enctype="multipart/form-data" >
+  <input type="hidden" name="_csrf" value="{{ csrf }}" />
+  <table width="80%" border="0" cellspacing="1px" cellpadding="0">
+    <tr>
+    <td valign="top"><strong>Rules:</strong></td>
+    <td style="padding-left:3px;" valign="top">Gore, CP, Spam, Nazi, Porn = Ban <br /><br />
+	</td>
+  </tr>
+  <tr>
+    <td valign="top"><strong>Image:</strong></td>
+    <td valign="top"><input type="file" name="image" accept="image/jpeg,image/png,image/gif" style="color: #000; background-color: #fff;"/><br /></td>
+  </tr>
+  <tr>
+    <td valign="top"><strong>or Url:</strong></td>
+    <td valign="top"><input type="text" name="url" value=""/><br /></td>
+  </tr>
+  <tr>
+    <td valign="top"><strong>Comment:</strong></td>
+    <td valign="top"><textarea id="content_comment" name="ucomment" rows="3" cols="30"></textarea><br /></td>
+  </tr>
+  <tr>
+    <td>&nbsp;</td>
+    <td align="right"><input type="submit" name="upload" value="Upload" /></td>
+  </tr>
+</table>
+    <input type="hidden" id="q" value="upload" />
+    </form>
+
+{%- endif %}