feat: Improve analytics charts readability and zone/source UX polish

[666mxvbee]

Summary

• improved analytics charts readability with axis labels, grid lines, tick labels, and point aggregation
• made analytics granularity actually affect chart rendering for legacy /occupancy and /forecasts data
• added interactive chart tooltips with hover/click behavior for line charts
• removed zone creation flow from the Zones page so zones are created only through a specific camera
• cleaned up zone UI labels and removed unnecessary Partner ID controls
• added horizontal scrolling to the Sources table
• fixed camera filter submit on Enter
• fixed active zone handles so they remain draggable above overlapping polygons