Fix TypeScript errors, Next.js 16 compatibility, and Vercel deployment (Prisma schema sync)

Co-authored-by: syed-reza98 <71028588+syed-reza98@users.noreply.github.com>

Author: Copilot

VERCEL_DEPLOYMENT_FIX.md

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+# Vercel Deployment Fix - PostgreSQL Schema Sync
+
+## Issue
+Vercel deployment failed with the following error:
+```
+Type error: Module '"@prisma/client"' has no exported member 'AuditLog'.
+```
+
+## Root Cause Analysis
+
+The codebase maintains two Prisma schema files:
+1. `prisma/schema.sqlite.prisma` - For local development (SQLite)
+2. `prisma/schema.postgres.prisma` - For production deployments (PostgreSQL)
+
+The PostgreSQL schema was **out of sync** with the SQLite schema. Specifically, it was missing:
+- `AuditLog` model (26 lines)
+- `InventoryLog` model (21 lines)
+- Related relations in User, Store, and Product models
+
+When Vercel built the application using the PostgreSQL schema, the Prisma client generated didn't include the `AuditLog` and `InventoryLog` types, causing the TypeScript compilation to fail.
+
+## Files Affected
+
+### Service Files Using AuditLog
+- `src/lib/services/audit-log.service.ts` - Imports `AuditLog` type from `@prisma/client`
+
+### Service Files Using InventoryLog
+- `src/lib/services/inventory.service.ts` - Uses `InventoryLog` for tracking inventory changes
+
+## Solution
+
+### 1. Added InventoryLog Model
+```prisma
+model InventoryLog {
+  id          String   @id @default(cuid())
+  storeId     String
+  productId   String
+  product     Product  @relation("InventoryLogs", fields: [productId], references: [id], onDelete: Cascade)
+  
+  previousQty Int
+  newQty      Int
+  changeQty   Int
+  reason      String
+  note        String?
+  
+  userId      String?
+  user        User?    @relation("InventoryUserLogs", fields: [userId], references: [id], onDelete: SetNull)
+  
+  createdAt   DateTime @default(now())
+  
+  @@index([storeId, productId, createdAt])
+  @@index([productId, createdAt])
+  @@index([userId, createdAt])
+}
+```
+
+### 2. Added AuditLog Model
+```prisma
+model AuditLog {
+  id        String   @id @default(cuid())
+  storeId   String?
+  store     Store?   @relation(fields: [storeId], references: [id], onDelete: Cascade)
+
+  userId    String?
+  user      User?    @relation("AuditUserLogs", fields: [userId], references: [id], onDelete: SetNull)
+
+  action    String   // e.g., "CREATE", "UPDATE", "DELETE"
+  entityType String  // e.g., "Product", "Order", "User"
+  entityId  String
+  
+  changes   String?  // JSON { "field": { "old": "value", "new": "value" } }
+  
+  ipAddress String?
+  userAgent String?
+
+  createdAt DateTime @default(now())
+
+  @@index([storeId, createdAt])
+  @@index([userId, createdAt])
+  @@index([entityType, entityId, createdAt])
+  @@map("audit_logs")
+}
+```
+
+### 3. Added Missing Relations
+
+**User Model:**
+```prisma
+inventoryLogs InventoryLog[] @relation("InventoryUserLogs")
+auditLogs     AuditLog[]     @relation("AuditUserLogs")
+```
+
+**Store Model:**
+```prisma
+auditLogs AuditLog[]
+```
+
+**Product Model:**
+```prisma
+inventoryLogs InventoryLog[] @relation("InventoryLogs")
+```
+
+## Verification
+
+### Before Fix:
+- PostgreSQL schema: **19 models**
+- SQLite schema: **21 models**
+- ❌ Schemas out of sync
+
+### After Fix:
+- PostgreSQL schema: **21 models** ✅
+- SQLite schema: **21 models** ✅
+- ✅ Schemas in sync
+
+## Deployment Notes
+
+1. **Automatic Migration:** When Vercel deploys, it will automatically run `prisma migrate deploy` which will create the new tables
+2. **No Data Loss:** New tables are being added, no existing data is modified
+3. **Backward Compatible:** The changes are additive only
+
+## Prevention
+
+To prevent schema drift in the future:
+1. Always update **both** schema files when adding new models
+2. Run validation on both schemas in CI/CD
+3. Consider using a single schema with conditional configuration
+4. Add a pre-commit hook to check schema parity
+
+## Commit
+
+- **Hash:** `6ac6cc6`
+- **Message:** Fix Vercel deployment: Add missing AuditLog and InventoryLog models to PostgreSQL schema
+- **Files Changed:** `prisma/schema.postgres.prisma` (+55 lines)