feat: Implement map analytics system with effectiveness tracking

Add complete map analytics pipeline to answer: "Which maps drive the most
players? Is my rotation working?"

Backend Changes:
- Migration 005: Add map_id FK to server_stats and wipe_history tables
- Stats consumer now captures current_map_id when persisting stats
- Map analytics queries: get_map_analytics() returns performance metrics,
  effectiveness scores, and rotation health
- API endpoint: GET /api/analytics/maps?range=90d returns summary with
  best performing map and rotation effectiveness percentage

Frontend Changes:
- MapAnalyticsView.vue: Complete dashboard with performance charts,
  sortable metrics table, actionable insights, and CSV export
- ECharts bar chart comparing avg vs peak players per map
- Color-coded effectiveness scoring (green ≥80%, yellow ≥60%, red <60%)
- Time range selector: 30d/90d/all

Purpose: Enables data-driven map selection for wipe day based on player
engagement metrics. Rotation effectiveness algorithm scores maps by
(avg_players / peak_players) * 100.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

backend/src/services/stats_consumer.rs

@@ -73,6 +73,11 @@ impl StatsConsumerService {
                                     // Parse JSON payload
                                     match serde_json::from_slice::<StatsPayload>(&msg.payload) {
                                         Ok(stats_payload) => {
+                                            // Fetch current map_id for map analytics tracking
+                                            let map_id = stats::get_current_map_id(&db, stats_payload.license_id)
+                                                .await
+                                                .unwrap_or(None);
+
                                             // Persist to database
                                             match stats::insert_server_stats(
                                                 &db,
@@ -83,6 +88,7 @@ impl StatsConsumerService {
                                                 stats_payload.entities,
                                                 stats_payload.uptime,
                                                 stats_payload.memory,
+                                                map_id,
                                             )
                                             .await
                                             {