feat: add click-to-copy CopyableCode component across all detail pages

- New CopyableCode component with monospace styling and click-to-copy
- TaskDetailPage: copyable task code in header
- ProjectDetailPage: copyable project code in header
- MilestoneDetailPage: copyable milestone code in header
- MeetingDetailPage: copyable meeting code in header
- SupportDetailPage: copyable support code in header
- ProposeDetailPage: copyable propose code in header and info section

Helps users easily copy resource codes for CLI usage (hf task get <code>, etc)

src/pages/ProjectDetailPage.tsx

@@ -6,6 +6,7 @@ import dayjs from 'dayjs'
 import { useAuth } from '@/hooks/useAuth'
 import ProjectFormModal from '@/components/ProjectFormModal'
 import MilestoneFormModal from '@/components/MilestoneFormModal'
+import CopyableCode from '@/components/CopyableCode'
 
 export default function ProjectDetailPage() {
   const { id } = useParams()
@@ -74,7 +75,7 @@ export default function ProjectDetailPage() {
       <button className="btn-back" onClick={() => navigate('/projects')}>← Back to projects</button>
 
       <div className="task-header">
-        <h2>📁 {project.name} {project.project_code && <span className="badge">{project.project_code}</span>}</h2>
+        <h2>📁 {project.name} {project.project_code && <CopyableCode code={project.project_code} />}</h2>
         <p style={{ color: 'var(--text-dim)', marginTop: 4 }}>{project.description || 'No description'}</p>
         {project.repo && <p style={{ color: 'var(--text-dim)', marginTop: 4 }}>📦 {project.repo}</p>}
         <div className="text-dim">Owner: {project.owner_name || 'Unknown'}</div>