fix(cache): address code review issues

- Add authentication to /api/cache/entries (GET and DELETE)
- Add authentication to /api/cache (GET and DELETE)
- Validate trendHours: clamp to 1-720 range
- Fix estimatedCostSaved bug: use calculated value instead of hardcoded 0

src/app/api/cache/entries/route.ts

@@ -1,5 +1,6 @@
 import { NextRequest, NextResponse } from "next/server";
 import { getDbInstance } from "@/lib/db/core";
+import { isAuthenticated } from "@/shared/utils/apiAuth";
 
 interface CacheEntry {
   id: string;
@@ -12,6 +13,10 @@ interface CacheEntry {
 }
 
 export async function GET(req: NextRequest) {
+  if (!(await isAuthenticated(req))) {
+    return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+  }
+
   try {
     const { searchParams } = new URL(req.url);
     const page = Math.max(1, parseInt(searchParams.get("page") || "1", 10));
@@ -71,6 +76,10 @@ export async function GET(req: NextRequest) {
 }
 
 export async function DELETE(req: NextRequest) {
+  if (!(await isAuthenticated(req))) {
+    return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+  }
+
   try {
     const { searchParams } = new URL(req.url);
     const signature = searchParams.get("signature");

src/app/api/cache/route.ts

@@ -9,15 +9,21 @@ import {
 } from "@/lib/semanticCache";
 import { getIdempotencyStats } from "@/lib/idempotencyLayer";
 import { getCacheMetrics, getCacheTrend } from "@/lib/db/settings";
+import { isAuthenticated } from "@/shared/utils/apiAuth";
 
 function errorMessage(error: unknown): string {
   return error instanceof Error ? error.message : String(error);
 }
 
 export async function GET(req: NextRequest) {
+  if (!(await isAuthenticated(req))) {
+    return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+  }
+
   try {
     const { searchParams } = new URL(req.url);
-    const trendHours = parseInt(searchParams.get("trendHours") || "24", 10);
+    const rawHours = parseInt(searchParams.get("trendHours") || "24", 10);
+    const trendHours = Math.min(720, Math.max(1, Number.isNaN(rawHours) ? 24 : rawHours));
 
     const cacheStats = getCacheStats();
     const idempotencyStats = getIdempotencyStats();
@@ -36,6 +42,10 @@ export async function GET(req: NextRequest) {
 }
 
 export async function DELETE(req: NextRequest) {
+  if (!(await isAuthenticated(req))) {
+    return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+  }
+
   try {
     const { searchParams } = new URL(req.url);
     const model = searchParams.get("model");

src/lib/db/settings.ts

@@ -630,7 +630,7 @@ export async function getCacheMetrics() {
       totalCachedTokens: totalsRow?.totalCachedTokens || 0,
       totalCacheCreationTokens: totalsRow?.totalCacheCreationTokens || 0,
       tokensSaved,
-      estimatedCostSaved: 0, // Would need pricing data to calculate
+      estimatedCostSaved,
       byProvider,
       byStrategy,
       lastUpdated: new Date().toISOString(),