Phase 6: rules editor + unsubscribe detection (AUD-72)

- FR-11 rules editor: plain-text area at /rules, saved and versioned
  (SaveRules appends a version; restore re-saves an old version), parse
  errors surfaced, one-click re-classify. The reply model now reads the
  rules document too (FR-11).
- FR-7 unsubscribe: parse and store List-Unsubscribe / List-Unsubscribe-Post
  (migration v6), detect email and web links (internal/unsubscribe), a
  domain-level ignore list, and an explicit record of what was marked. No
  code path contacts an unsubscribe link; acting on one needs Sam's approval.
- Migration v6 is additive; unsubscribe gains url/updated_at.
- Tests: detector, parser, store migration/records/candidates, rules editor,
  unsubscribe handlers, message-detail rendering.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

web/templates/message.html

@@ -13,6 +13,18 @@
     </div>
   </div>
 
+  {{if .UnsubLinks}}
+  <section class="unsub-detected" aria-label="Unsubscribe">
+    <h3>Unsubscribe</h3>
+    {{if eq .UnsubStatus "ignored"}}<span class="pill">ignored</span>{{end}}
+    {{if eq .UnsubStatus "done"}}<span class="pill">recorded</span>{{end}}
+    <ul class="unsub-link-list">
+      {{range .UnsubLinks}}<li><span class="pill">{{.Method}}</span> <span class="unsub-url">{{.URL}}</span></li>{{end}}
+    </ul>
+    <a class="btn btn-utility btn-small" href="/unsubscribe">Manage unsubscribe</a>
+  </section>
+  {{end}}
+
   <details class="detail-original" open>
     <summary>Original message</summary>
     <pre class="detail-text">{{.Message.BodyText}}</pre>