Kanban board, Project Management, Proposals/Quotes, Time Tracking, Custom Fields

- Kanban board with drag-and-drop per stage, colour-coded cards, score bars
- Project Management with milestones, Gantt timeline, inline add milestone/task
- Proposal/Quote builder with line items, VAT, terms, e-signature capture
- Time Tracking with stopwatch, manual entry, hours-by-project chart
- Custom Fields system: admin-defined fields per entity (leads/customers/
  projects/opportunities) with drag-and-drop reordering in settings
- Reusable CustomFieldsSection component for entity detail pages
- Customers API endpoint
- All builds pass with zero errors

src/app/api/leads/[id]/route.ts

@@ -28,6 +28,7 @@ export async function GET(request: NextRequest, { params }: { params: Promise<{
     const result = await query(
       `SELECT l.id, l.company_name, l.contact_name, l.email, l.phone, l.score,
               l.assigned_to, l.created_at, l.updated_at, l.notes, l.source_id,
+              l.custom_fields,
               ls.name AS stage_name,
               u.id AS user_id, u.first_name, u.last_name, u.email AS user_email, u.avatar_url
        FROM leads l
@@ -59,6 +60,7 @@ export async function GET(request: NextRequest, { params }: { params: Promise<{
         email: r.user_email,
         avatar: avatarSvgUrl(`${r.first_name} ${r.last_name}`),
       } : null,
+      customFields: r.custom_fields || {},
       createdAt: r.created_at,
       updatedAt: r.updated_at,
     }
@@ -135,6 +137,10 @@ export async function PATCH(request: NextRequest, { params }: { params: Promise<
       fields.push(`score = $${idx++}`)
       values.push(score)
     }
+    if (body.customFields !== undefined) {
+      fields.push(`custom_fields = $${idx++}`)
+      values.push(JSON.stringify(body.customFields))
+    }
 
     if (fields.length === 0) {
       return NextResponse.json({ error: "No fields to update" }, { status: 400 })