fix(lint): resolve eslint warnings, type errors and clean unused code

lib/auth.ts

@@ -1,11 +1,16 @@
-import { SignJWT, jwtVerify } from 'jose';
+import { SignJWT, jwtVerify, type JWTPayload } from 'jose';
 import { cookies } from 'next/headers';
 import { NextRequest, NextResponse } from 'next/server';
 
 const secretKey = process.env.JWT_SECRET || 'super-secret-key-replace-me-in-production';
 const key = new TextEncoder().encode(secretKey);
 
-export async function encrypt(payload: any) {
+export interface SessionPayload extends JWTPayload {
+  userId?: string;
+  expires?: Date;
+}
+
+export async function encrypt(payload: JWTPayload) {
   return await new SignJWT(payload)
     .setProtectedHeader({ alg: 'HS256' })
     .setIssuedAt()
@@ -13,13 +18,13 @@ export async function encrypt(payload: any) {
     .sign(key);
 }
 
-export async function decrypt(input: string): Promise<any> {
+export async function decrypt(input: string): Promise<JWTPayload | null> {
   try {
     const { payload } = await jwtVerify(input, key, {
       algorithms: ['HS256'],
     });
     return payload;
-  } catch (error) {
+  } catch {
     return null;
   }
 }
@@ -53,16 +58,17 @@ export async function updateSession(request: NextRequest) {
   const session = request.cookies.get('session')?.value;
   if (!session) return;
 
-  const parsed = await decrypt(session);
+  const parsed = (await decrypt(session)) as SessionPayload | null;
   if (!parsed) return;
   
-  parsed.expires = new Date(Date.now() + 24 * 60 * 60 * 1000);
+  const expires = new Date(Date.now() + 24 * 60 * 60 * 1000);
+  parsed.expires = expires;
   const res = NextResponse.next();
   res.cookies.set({
     name: 'session',
     value: await encrypt(parsed),
     httpOnly: true,
-    expires: parsed.expires,
+    expires: expires,
   });
   return res;
 }