#4320 Add attendance data graph types to statistics tab

[RemainingDelta]

Changes

• Add ATTENDANCE_BY_TEAM and ATTENDANCE_BY_DIVISION graph types — compute the percentage of a team's roster (members + leads + head) that attended its meetings, aggregated per team or per division with the Sum/Avg toggle
• Add two new Graph_Type enum values + migration, mirrored in the shared GraphType enum
• Add getGraphDataForAttendanceByTeam/ByDivision in statistics.utils.ts, wired into the getGraphData/getAxisLabels switches
• Extract the team-attendance-percent formula (previously copy-pasted in the attendance transformer + service) into a shared attendance.utils.ts used by all call sites
• Register the new types in graphs.factory.ts (every collection gets one; one showcase collection gets both), and draw meeting attendees from each team's real roster so percentages are meaningful

Notes

• Attendance graphs ignore the car filter — Meeting_Attendance has no car relation, so carIds is a no-op for these types
• Only Team and Division dimensions exist (no "by Project") since meetings aren't tied to projects
• Only closed sessions (closedAt set) within the graph's date range are counted; open sessions are excluded
• No frontend changes needed — the graph dropdown and chart rendering are already enum-driven

Screenshots

Old Dropdown:

New Dropdown:

Old Graphs:

New Graphs:

Closes #4320

[staysgt]

Looks good so far! Left a few comments