poi-index: map-core selectors, planner.pois schema, /api/pois route + client, metrics

Replace the planner's Overpass proxy with a self-hosted POI index:
- map-core POI categories become structured tag selectors (single source of
  truth) + osmium filter / classification helpers
- planner.pois PostGIS table (centroid points, GiST + category indexes)
- /api/pois serving route (session + same-origin + rate limit, 100 cap)
- lib/pois.ts client (renamed from overpass.ts; GET, quantized bbox)
- metrics: poi_api_requests_total + DB-collected index rows/age gauges;
  drop overpass_* metrics
- remove /api/overpass proxy + dead OVERPASS_URLS on the planner service
  (Journal surface backfill still uses it via code default)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/db/src/schema/planner.ts

@@ -1,4 +1,4 @@
-import { pgSchema, text, timestamp, boolean, customType, index } from "drizzle-orm/pg-core";
+import { pgSchema, text, timestamp, boolean, jsonb, customType, index, primaryKey } from "drizzle-orm/pg-core";
 
 const bytea = customType<{ data: Buffer }>({
   dataType() {
@@ -6,6 +6,15 @@ const bytea = customType<{ data: Buffer }>({
   },
 });
 
+// Centroid point in WGS84. Ways/relations are reduced to their centroid at
+// extract time (matching the old Overpass `out center`), so every POI is a
+// single point regardless of its OSM geometry.
+const point = customType<{ data: string }>({
+  dataType() {
+    return "geometry(Point, 4326)";
+  },
+});
+
 export const plannerSchema = pgSchema("planner");
 
 export const sessions = plannerSchema.table("sessions", {
@@ -22,3 +31,30 @@ export const sessions = plannerSchema.table("sessions", {
   // total sessions ever created.
   lastActivityIdx: index("sessions_last_activity_idx").on(t.lastActivity),
 }));
+
+/**
+ * Self-hosted POI index. Fed monthly by the extract pipeline (osmium filter on
+ * the BRouter host) + the flagship import job's atomic staging swap — never
+ * written at request time. Served read-only by `/api/pois` for the planner's
+ * map overlays, replacing the former Overpass proxy.
+ *
+ * An OSM element that matches more than one category is stored once per
+ * category (part of the composite primary key), because the client treats each
+ * category's markers independently.
+ */
+export const pois = plannerSchema.table("pois", {
+  // OSM element type: 'n' (node), 'w' (way), or 'r' (relation).
+  osmType: text("osm_type").notNull(),
+  osmId: text("osm_id").notNull(),
+  category: text("category").notNull(),
+  name: text("name"),
+  geom: point("geom").notNull(),
+  tags: jsonb("tags").$type<Record<string, string>>().notNull(),
+  importedAt: timestamp("imported_at", { withTimezone: true }).notNull().defaultNow(),
+}, (t) => ({
+  pk: primaryKey({ columns: [t.osmType, t.osmId, t.category] }),
+  // GiST spatial index for the bbox intersection in the serving query.
+  geomIdx: index("pois_geom_idx").using("gist", t.geom),
+  // btree on category so `category = ANY($cats)` is index-driven.
+  categoryIdx: index("pois_category_idx").on(t.category),
+}));