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/dashboard.html

@@ -26,6 +26,8 @@
   <header class="nav-bar">
     <span class="wordmark">Email Agent</span>
     <div class="nav-actions">
+      <a class="btn btn-utility" href="/rules">Rules</a>
+      <a class="btn btn-utility" href="/unsubscribe">Unsubscribe</a>
       <button class="btn btn-utility theme-toggle" type="button" onclick="eaToggleTheme()" aria-label="Toggle dark mode">
         <span class="icon-light" aria-hidden="true">&#9790;</span>
         <span class="icon-dark" aria-hidden="true">&#9728;</span>