Build observation analytics and trends dashboard

[bgorzelic]

Description

Add an analytics page that provides insights across all of a user's observations over time. This helps incident commanders identify patterns, track conditions across incidents, and prepare after-action reports.

Proposed Visualizations

Charts (use recharts or visx)

• EWS over time — line chart showing observed vs. predicted EWS across observations
• ROS distribution — histogram of rate of spread values
• Observation frequency — bar chart by month/week
• LCES compliance — donut chart showing % of observations with full LCES

Summary Stats

• Average/median EWS ratio across all observations
• Most common fuel types
• Highest recorded ROS
• Observations by status (draft/complete)

Filters

• Date range picker
• Incident name filter
• Status filter (draft/complete)

Acceptance Criteria

• New /analytics route accessible from sidebar
• At least 3 distinct chart types
• Responsive on mobile (charts scale down)
• Filters update charts in real time
• Works with 0 observations (empty state)
• Loading skeletons while data loads
• Accessible chart labels and descriptions