feat(kanban): tiempo maximo por columna con borde rojo (issue 0089)

Adds column-level max time limit. Cards whose time_in_column_ms exceeds
the limit show a red border + red halo. Columns marked as Done never
trigger the visual regardless of the limit (per spec).

Backend:
- Migration 011_column_max_time.sql adds columns.max_time_minutes
  INTEGER NOT NULL DEFAULT 0 (0 = no limit). Aditiva, idempotente.
- Column struct + ColumnPatch + UpdateColumn handle the new field;
  negatives clamp to 0; listing query includes it.
- handleUpdateColumn (PATCH /api/columns/:id) accepts max_time_minutes
  in the JSON body.

Frontend:
- Column TS interface + UpdateColumnInput updated.
- KanbanColumn context menu: new entry "Tiempo maximo" using
  window.prompt for low-friction config; shows current value when >0.
- KanbanCard receives columnOverdue prop calculated from the column
  state and card.time_in_column_ms; renders red border (var
  --mantine-color-red-6) with 2px width + 2px red halo when overdue.
- data-card-id, data-column-overdue, data-locked attributes on the card
  paper element so e2e tests / scripts can query state.

Tests: TestColumnMaxTimeMinutes_Defaults + _Update verify the schema
default, the clamp on negative input, and that updating max_time leaves
other fields untouched.

Visual regression of the red border kept out of automated e2e because
it requires either clock control or real cards aged > N minutes; will be
verified manually after merge.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/components/KanbanColumn.tsx

@@ -25,6 +25,7 @@ import {
   IconCheckbox,
   IconChevronDown,
   IconChevronRight,
+  IconClock,
   IconDotsVertical,
   IconGripVertical,
   IconPencil,
@@ -47,6 +48,7 @@ interface Props {
   onMoveColumnLocation: (id: string, location: "board" | "sidebar") => void;
   onDeleteColumn: (id: string) => void;
   onSetWIPLimit: (id: string, limit: number) => void;
+  onSetMaxTimeMinutes: (id: string, minutes: number) => void;
   onToggleDone: (id: string, is_done: boolean) => void;
   onEditCard: (card: Card) => void;
   onDeleteCard: (id: string) => void;
@@ -80,6 +82,7 @@ function KanbanColumnImpl({
   onMoveColumnLocation,
   onDeleteColumn,
   onSetWIPLimit,
+  onSetMaxTimeMinutes,
   onToggleDone,
   onEditCard,
   onDeleteCard,
@@ -390,6 +393,24 @@ function KanbanColumnImpl({
                   >
                     {column.is_done ? "Quitar marca Done" : "Marcar como Done"}
                   </Menu.Item>
+                  <Menu.Item
+                    leftSection={<IconClock size={14} />}
+                    data-test="column-max-time"
+                    onClick={() => {
+                      const current = column.max_time_minutes || 0;
+                      const raw = window.prompt(
+                        "Tiempo maximo en minutos (0 = sin limite). Cards que pasen este tiempo en la columna mostraran borde rojo. Columnas Done no aplican.",
+                        String(current)
+                      );
+                      if (raw === null) return;
+                      const v = parseInt(raw.trim(), 10);
+                      const safe = Number.isFinite(v) && v >= 0 ? v : 0;
+                      if (safe !== current) onSetMaxTimeMinutes(column.id, safe);
+                    }}
+                  >
+                    Tiempo maximo
+                    {column.max_time_minutes > 0 ? ` (${column.max_time_minutes} min)` : ""}
+                  </Menu.Item>
                   <Menu.Item
                     leftSection={<ArchiveIcon size={14} />}
                     onClick={() => onMoveColumnLocation(column.id, isInSidebar ? "board" : "sidebar")}
@@ -435,6 +456,11 @@ function KanbanColumnImpl({
                     users={users}
                     assignee={c.assignee_id ? usersById.get(c.assignee_id) : undefined}
                     inDoneColumn={column.is_done}
+                    columnOverdue={
+                      !column.is_done &&
+                      column.max_time_minutes > 0 &&
+                      c.time_in_column_ms > column.max_time_minutes * 60_000
+                    }
                     highlight={highlightCardId === c.id}
                     activeSticker={activeSticker}
                     onAddSticker={onAddSticker}