fix: resolve all 69 ESLint warnings across 40 files

- Remove unused imports (Mail, CalendarIcon, Plus, Circle, cn, Link,
  MessageCircle, User, Tag, FolderUp, useEffect, LogOut, GripVertical,
  Check, X, HoverActionsMode, HoverActionsCorner, asn1js, Convert, etc.)
- Prefix unused variables/params with underscore to satisfy no-unused-vars
- Add missing React hook dependencies (exhaustive-deps)
- Wrap handleNavigateUp in useCallback and selectedGroupMembers in useMemo
- Remove unused eslint-disable directives in jmap/client.ts
- Replace as any with typed casts in filter-store and smime-store tests
- Remove dead code (macOk assignment, unused now variable)

components/email/thread-conversation-view.tsx

@@ -305,7 +305,7 @@ function EmailCard({
       cancelled = true;
       objectUrls.forEach(url => URL.revokeObjectURL(url));
     };
-  }, [client, email?.id]);
+  }, [client, email?.id, email?.attachments]);
 
   // Sanitize and prepare email HTML content
   const emailContent = useMemo(() => {