refactor: migrate scorecards and pricing to createLazyStatements

Replace manual 'let _stmts = null; function getStatements()' pattern
with the shared createLazyStatements() factory from lib/lazy-statements.js.

This aligns scorecards.js and pricing.js with the convention already
used in analytics.js, sessions.js, leaderboard.js, and postmortem.js,
reducing boilerplate and eliminating the direct getDb() import in
scorecards.js (pricing.js still needs it for transactions/seeding).

Author: sauravbhattacharya001

backend/routes/pricing.js

@@ -10,6 +10,7 @@ const { getDb } = require("../db");
 const { sanitizeString } = require("../lib/validation");
 const { requireSessionId, wrapRoute } = require("../lib/request-helpers");
 const { invalidatePricingCache } = require("../lib/pricing");
+const { createLazyStatements } = require("../lib/lazy-statements");
 
 const router = express.Router();
 
@@ -33,13 +34,7 @@ const DEFAULT_PRICING = {
 };
 
 // ── Cached prepared statements ──────────────────────────────────────
-let _pricingStmts = null;
-
-function getPricingStatements() {
-  if (_pricingStmts) return _pricingStmts;
-  const db = getDb();
-
-  _pricingStmts = {
+const getPricingStatements = createLazyStatements((db) => ({
     getAll: db.prepare("SELECT * FROM model_pricing ORDER BY model ASC"),
     getByModel: db.prepare("SELECT * FROM model_pricing WHERE model = ?"),
     upsert: db.prepare(`
@@ -56,10 +51,7 @@ function getPricingStatements() {
     getSessionEvents: db.prepare(
       "SELECT event_id, event_type, model, tokens_in, tokens_out, duration_ms, timestamp FROM events WHERE session_id = ? ORDER BY timestamp ASC"
     ),
-  };
-
-  return _pricingStmts;
-}
+}));
 
 /**
  * Ensure default pricing entries exist in the DB.

backend/routes/scorecards.js

@@ -1,6 +1,6 @@
 const express = require("express");
-const { getDb } = require("../db");
 const { wrapRoute, parseDays, daysAgoCutoff } = require("../lib/request-helpers");
+const { createLazyStatements } = require("../lib/lazy-statements");
 
 const router = express.Router();
 
@@ -32,15 +32,9 @@ function clamp(v, lo, hi) { return Math.max(lo, Math.min(hi, v)); }
 function round2(v) { return Math.round(v * 100) / 100; }
 
 // ── Cached prepared statements for scorecards ───────────────────────
-// Lazily initialized once, reused across all requests to avoid
-// re-compiling SQL on every call.
-let _scorecardStmts = null;
-
-function getScorecardStatements() {
-  if (_scorecardStmts) return _scorecardStmts;
-  const db = getDb();
-
-  _scorecardStmts = {
+// Uses createLazyStatements for consistent lazy-init pattern across
+// all route files (same approach as analytics.js, sessions.js, etc.).
+const getScorecardStatements = createLazyStatements((db) => ({
     agentStats: db.prepare(`
       SELECT
         agent_name,
@@ -127,10 +121,7 @@ function getScorecardStatements() {
       GROUP BY day
       ORDER BY day
     `),
-  };
-
-  return _scorecardStmts;
-}
+}));
 
 // ── GET /scorecards ─────────────────────────────────────────────────
 // Returns per-agent scorecards with composite score, letter grade,