feat: implement FTPS deployment script

Add automated deployment script that uploads the Hugo-built site to
www.markusgraf.ch via FTPS. Implementation includes:

- scripts/deploy.sh: Deployment script with full functionality
  - Prerequisite checks (public/, lftp, FTPS_PASSWORD)
  - FTPS connection with SSL/TLS to www.markusgraf.ch
  - Mirror upload from public/ to httpsdocs/ with parallel transfers
  - Colored output with progress reporting
  - Comprehensive error handling with actionable messages

- DEPLOYMENT.md: Complete deployment documentation
  - Setup instructions and prerequisites
  - Usage examples and workflow
  - Security best practices
  - Troubleshooting guide

- .gitignore: Add entries for .env files to prevent credential leaks

- tasks.md: Mark all implementation tasks as completed

All spec requirements satisfied:
- FTPS Deployment Script provided (scripts/deploy.sh:1)
- Secure Credential Management via environment variables
- Deployment Status Feedback with colored output
- Deployment Prerequisites verified before upload

Tested with missing prerequisites, all checks working correctly.

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

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

.gitignore

@@ -31,3 +31,8 @@ package-lock.json
 /tests/visual/screenshots/
 /tests/visual/diffs/
 /tests/visual/actual/
+
+# Environment and credential files
+.env
+.env.*
+!.env.example