fix(nav): register Journal/Planner shapes, fix headerColor crash, enable academic week expansion

Bugs fixed:
- 'cc-teacher-timetable-node' missing from NODE_TYPE_THEMES caused
  Cannot read properties of undefined (reading 'headerColor') crash
  when clicking My Timetable
- 'cc-journal-node' and 'cc-planner-node' had no shape utils registered,
  causing 'No shape util found for type' error on Journal/Planner click
- Added null safety (?? fallback) to getNodeTheme to prevent future crashes
  from any other unmapped type
- Removed AcademicWeek from canExpand exclusion so weeks can be expanded
  to show individual academic days

Added:
- CCJournalNodeShapeUtil and CCPlannerNodeShapeUtil (stub shapes)
- CCJournalNodeProps and CCPlannerNodeProps types
- Journal/Planner added to CCNodeTypes, ccGraphShapeProps, NODE_TYPE_THEMES
- 'cc-department-structure-node' mapping added to NODE_TYPE_THEMES

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

src/utils/tldraw/ui-overrides/components/shared/navigation/CCGraphNavPanel.tsx

@@ -137,7 +137,6 @@ function TreeItem({ node, depth, onSelect, onExpand }: TreeItemProps) {
 
     const canExpand = node.has_children !== false
         && node.node_type !== 'CalendarDay'
-        && node.node_type !== 'AcademicWeek'
         && node.status !== 'empty'
         && node.status !== 'no_school'
         && node.status !== 'not_initialized';