feat: Add practical use case examples and comprehensive gap analysis

- Created invoice template demonstrating business document requirements
- Added design pattern example showing knowledge management use case
- Included sample data file for template + data scenarios
- Comprehensive gap analysis identifying 6 critical tooling limitations
- Documented 3-phase development roadmap for enhanced capabilities
- Based on Issue #63 use case brainstorming requirements

Key gaps identified:
1. Template engine for dynamic document generation
2. Calculation system for mathematical operations
3. Batch processing for multi-document workflows
4. External data integration capabilities
5. Cross-document relationship management
6. Advanced output format support

Ready for requirements engineering and epic decomposition.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

examples/invoice_data.json

@@ -0,0 +1,37 @@
+{
+  "invoice_number": "INV-2025-001",
+  "date": "2025-10-02",
+  "due_date": "2025-11-01",
+  "currency": "EUR",
+  "tax_rate": 0.19,
+  "tax_rate_percent": "19",
+  "customer": {
+    "company": "Acme Corporation",
+    "contact": "John Smith",
+    "address": "123 Business Ave, 54321 Commerce City",
+    "email": "john.smith@acme.example"
+  },
+  "line_items": [
+    {
+      "description": "MarkiTect Pro License (1 year)",
+      "quantity": 5,
+      "unit_price": 299.00,
+      "total": 1495.00
+    },
+    {
+      "description": "Implementation & Training",
+      "quantity": 40,
+      "unit_price": 150.00,
+      "total": 6000.00
+    },
+    {
+      "description": "Priority Support Package",
+      "quantity": 1,
+      "unit_price": 500.00,
+      "total": 500.00
+    }
+  ],
+  "subtotal": 7995.00,
+  "tax_amount": 1519.05,
+  "total": 9514.05
+}