feat: add SQLite persistent storage for request logging

- Add SQLAlchemy-based database layer for persistent storage
  - Create models for access_logs, credential_attempts, attack_detections, ip_stats
  - Include fields for future GeoIP and reputation enrichment
  - Implement sanitization utilities to protect against malicious payloads
  - Fix XSS vulnerability in dashboard template (HTML escape all user data)
  - Add DATABASE_PATH and DATABASE_RETENTION_DAYS config options
  - Dual storage: in-memory for dashboard performance + SQLite for persistence

  New files:
  - src/models.py - SQLAlchemy ORM models
  - src/database.py - DatabaseManager singleton
  - src/sanitizer.py - Input sanitization and HTML escaping
  - requirements.txt - SQLAlchemy dependency

  Security protections:
  - Parameterized queries via SQLAlchemy ORM
  - Field length limits to prevent storage exhaustion
  - Null byte and control character stripping
  - HTML escaping on dashboard output

requirements.txt

@@ -0,0 +1,5 @@
+# Krawl Honeypot Dependencies
+# Install with: pip install -r requirements.txt
+
+# Database ORM
+SQLAlchemy>=2.0.0,<3.0.0