# Fix Login Error - JSON.parse unexpected character

## Problem
Error: `JSON.parse: unexpected character at line 1 column 1 of the JSON data`

This error occurred when trying to login because:
1. Database was missing required columns (`email_verified`, `school_id`, `preferred_language`)
2. Middleware was returning HTML error pages instead of JSON for API endpoints
3. Frontend was not handling non-JSON responses

## Solution Applied

### 1. Database Fix
Added missing columns to `users` table:
```sql
ALTER TABLE users ADD COLUMN email_verified BOOLEAN NOT NULL DEFAULT FALSE;
ALTER TABLE users ADD COLUMN school_id INT NULL;
ALTER TABLE users ADD COLUMN preferred_language VARCHAR(10) NULL DEFAULT 'id';
```

Run: `python scripts/fix_database.py`

### 2. Backend Improvements

#### app/middleware.py
- Added JSON response handling for API endpoints when errors occur
- Returns proper JSON error messages instead of HTML error pages

#### app/blueprints/auth.py
- Added try-catch for `request.get_json()` to handle malformed JSON
- Uses `force=True, silent=True` for more robust JSON parsing

### 3. Frontend Improvement

#### app/static/dashboard.js
- Added content-type validation before parsing JSON response
- Shows user-friendly error message if server returns non-JSON response

## Testing
```bash
# Test login endpoint
python -c "
from app import create_app
from flask import json
app = create_app()
client = app.test_client()
response = client.post('/api/login', 
    data=json.dumps({'email': 'admin@aldudu.com', 'password': 'test'}),
    content_type='application/json'
)
print(response.get_json())
"
```

## Prevention
To prevent this issue in the future:
1. Always run migrations after deployment: `flask db upgrade`
2. Use the fix script if migrations fail: `python scripts/fix_database.py`
3. Check database schema matches models: `python scripts/check_migrations.py`

## Files Changed
- `app/middleware.py` - Added JSON error handling
- `app/middleware/tenant.py` - Added JSON error handling
- `app/blueprints/auth.py` - Added robust JSON parsing
- `app/static/dashboard.js` - Added response validation
- `scripts/fix_database.py` - New script to fix missing columns
- `scripts/fix_email_verified_column.py` - Updated script