perf(analytics): collapse 30-day occupancy timeline into single GROUP BY query

The dashboard's occupancy-timeline metric was firing N separate queries
(one per day, 30 for .30d / 90 for .90d) that saturated the postgres pool
and stalled every other request in the app. Replace with a single query
using generate_series for the date range + LEFT JOIN onto active
reservations + COUNT(DISTINCT berth_id) GROUP BY day.

Same data, ~30× fewer queries on .30d, ~90× fewer on .90d. The snapshot
cache layer still applies, so cached reads are still zero-DB.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/services/analytics.service.ts

@@ -11,7 +11,6 @@ import { db } from '@/lib/db';
 import { analyticsSnapshots } from '@/lib/db/schema/insights';
 import { interests } from '@/lib/db/schema/interests';
 import { invoices } from '@/lib/db/schema/financial';
-import { berthReservations } from '@/lib/db/schema/reservations';
 import { PIPELINE_STAGES } from '@/lib/constants';
 import {
   ALL_RANGES,
@@ -172,37 +171,45 @@ export async function computeOccupancyTimeline(
   range: DateRange,
 ): Promise<OccupancyTimelineData> {
   const { from, to } = rangeToBounds(range);
-  const days = Math.max(1, Math.ceil((to.getTime() - from.getTime()) / 86_400_000));
   // Total berths per port (current count - assumes no churn).
   const totalRow = await db.execute<{ total: number }>(
     sql`SELECT count(*)::int AS total FROM berths WHERE port_id = ${portId}`,
   );
   const total = totalRow[0]?.total ?? 0;
 
-  // For each day in range, count berths that have an active reservation
-  // covering that day. A reservation is "covering" if start_date <= day
-  // AND (end_date IS NULL OR end_date >= day). Walk forward from `from`
-  // so custom ranges produce the right calendar days, not just N
-  // most-recent days from "now".
-  const points: OccupancyTimelineData['points'] = [];
-  for (let i = 0; i < days; i++) {
-    const day = new Date(from.getTime() + i * 86_400_000);
-    const dayStr = day.toISOString().slice(0, 10);
-    const occRow = await db
-      .select({ occupied: sql<number>`count(distinct ${berthReservations.berthId})::int` })
-      .from(berthReservations)
-      .where(
-        and(
-          eq(berthReservations.portId, portId),
-          eq(berthReservations.status, 'active'),
-          sql`${berthReservations.startDate} <= ${dayStr}::date`,
-          sql`(${berthReservations.endDate} IS NULL OR ${berthReservations.endDate} >= ${dayStr}::date)`,
-        ),
-      );
-    const occupied = occRow[0]?.occupied ?? 0;
+  // Single-query implementation: generate_series for the date range and
+  // LEFT JOIN active reservations whose [start_date, end_date] window
+  // covers each day. Returns every day's occupancy count in one round
+  // trip; replaces the prior per-day loop that fired N queries (30 for
+  // .30d, 90 for .90d) and saturated the postgres pool.
+  const fromStr = from.toISOString().slice(0, 10);
+  const toStr = new Date(to.getTime() - 86_400_000).toISOString().slice(0, 10);
+  const rows = await db.execute<{ day: string; occupied: number }>(
+    sql`
+      WITH days AS (
+        SELECT generate_series(${fromStr}::date, ${toStr}::date, '1 day'::interval)::date AS day
+      ),
+      active_reservations AS (
+        SELECT berth_id, start_date, end_date
+        FROM berth_reservations
+        WHERE port_id = ${portId} AND status = 'active'
+      )
+      SELECT
+        to_char(days.day, 'YYYY-MM-DD') AS day,
+        COUNT(DISTINCT ar.berth_id)::int AS occupied
+      FROM days
+      LEFT JOIN active_reservations ar
+        ON ar.start_date <= days.day
+        AND (ar.end_date IS NULL OR ar.end_date >= days.day)
+      GROUP BY days.day
+      ORDER BY days.day
+    `,
+  );
+  const points: OccupancyTimelineData['points'] = rows.map((r) => {
+    const occupied = Number(r.occupied) || 0;
     const occupancyPct = total === 0 ? 0 : Math.round((occupied / total) * 1000) / 10;
-    points.push({ date: dayStr, occupied, total, occupancyPct });
-  }
+    return { date: r.day, occupied, total, occupancyPct };
+  });
   return { points };
 }