Add demo-03: CSV data processor with intentional code smells

- Add employee_data_processor.py: functional but ugly code with god function, globals, hardcoded values, mixed concerns
- Add employees.csv: sample data with 10 records (4 invalid for testing)
- Generates report.json and report.html output files
- Perfect candidate for refactoring demo

demo-03/report.json

@@ -0,0 +1,81 @@
+{
+  "summary": {
+    "total_employees": 6,
+    "skipped_records": 4,
+    "total_annual_payroll": 3984000,
+    "employees_by_department": {
+      "Engineering": 2,
+      "Human Resources": 2,
+      "Sales": 1,
+      "Marketing": 1
+    }
+  },
+  "employees": [
+    {
+      "name": "Alice Smith",
+      "email": "alice@example.com",
+      "department": "Engineering",
+      "annual_salary": 900000,
+      "hire_date": "2023-01-15",
+      "years_experience": 3.0
+    },
+    {
+      "name": "Diana Prince",
+      "email": "diana@example.com",
+      "department": "Engineering",
+      "annual_salary": 984000,
+      "hire_date": "2022-05-20",
+      "years_experience": 3.66
+    },
+    {
+      "name": "Eve Wilson",
+      "email": "eve@example.com",
+      "department": "Human Resources",
+      "annual_salary": 696000,
+      "hire_date": "2023-04-10",
+      "years_experience": 2.77
+    },
+    {
+      "name": "Grace Lee",
+      "email": "grace@example.com",
+      "department": "Sales",
+      "annual_salary": 0,
+      "hire_date": "2023-06-01",
+      "years_experience": 2.63
+    },
+    {
+      "name": "Ivy Chen",
+      "email": "ivy@example.com",
+      "department": "Marketing",
+      "annual_salary": 744000,
+      "hire_date": "2023-07-15",
+      "years_experience": 2.51
+    },
+    {
+      "name": "Jack Brown",
+      "email": "jack@example.com",
+      "department": "Human Resources",
+      "annual_salary": 660000,
+      "hire_date": "2023-08-01",
+      "years_experience": 2.46
+    }
+  ],
+  "skipped": [
+    {
+      "name": "Bob Jones",
+      "reason": "Negative salary"
+    },
+    {
+      "name": "Charlie",
+      "reason": "Invalid email"
+    },
+    {
+      "name": "Frank Miller",
+      "reason": "Invalid department"
+    },
+    {
+      "name": "Henry Davis",
+      "reason": "Invalid hire_date"
+    }
+  ]
+}