feat: work-in-progress limits and swimlanes on the board

Each status can carry a WIP limit in the project settings; the board shows
it next to the count, marks a column that goes over it and says so when a
card is dropped there. The board can also be grouped in rows by person,
epic, priority or type, remembered per browser.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/api/schema.gql

@@ -1009,6 +1009,11 @@ type WorkflowStatus {
 
   """Entering it needs a reason"""
   requiresReason: Boolean!
+
+  """
+  Work-in-progress limit: most tickets the column should hold (a warning, not a lock)
+  """
+  wipLimit: Int
 }
 
 input WorkflowStatusInput {
@@ -1018,4 +1023,7 @@ input WorkflowStatusInput {
   id: String!
   name: String!
   requiresReason: Boolean! = false
+
+  """Work-in-progress limit (null: none)"""
+  wipLimit: Int
 }