fix(build): resolve Turbopack performance issue with process.cwd()

The Turbopack build was matching 29409+ files due to dynamic path
resolution in upload.ts. This caused the CI build to hang.

Root cause: Turbopack traces process.cwd() and creates overly broad
file patterns, leading to performance issues.

Solution: Extract process.cwd() into a separate function to prevent
Turbopack from tracing the entire project directory.

This fix reduces build time and prevents CI timeout issues.

src/lib/upload.ts

@@ -3,6 +3,10 @@ import { existsSync } from 'fs';
 import path from 'path';
 import { nanoid } from 'nanoid';
 
+function getWorkingDirectory(): string {
+  return process.cwd();
+}
+
 export interface UploadOptions {
   maxSize?: number;
   allowedTypes?: string[];
@@ -130,7 +134,7 @@ export async function uploadFile(
 
   const uploadBaseDir = process.env.UPLOAD_DIR || './uploads';
   const datePath = getDatePath();
-  const uploadDir = path.join(process.cwd(), uploadBaseDir, type, datePath);
+  const uploadDir = path.join(getWorkingDirectory(), uploadBaseDir, type, datePath);
 
   if (!existsSync(uploadDir)) {
     await mkdir(uploadDir, { recursive: true });
@@ -184,7 +188,7 @@ export async function getFileInfo(filePath: string) {
       createdAt: stats.birthtime,
       modifiedAt: stats.mtime,
     };
-  } catch (error) {
+  } catch {
     return null;
   }
 }