docs: add security policy and deployment guide

- Add SECURITY.md with vulnerability reporting process
- Add comprehensive deployment guide (docs/deployment/index.md)
- Generate uv.lock for reproducible builds
- Update audit rules to check correct deployment path
- Remove Node.js dependency, use Tailwind CLI standalone

Resolves audit warnings:
- THIRD-DEP-001: Dependency lock file
- DOC-SEC-001: Security policy
- DOC-OPS-001: Deployment documentation

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

uv.lock

@@ -0,0 +1,8 @@
+version = 1
+revision = 3
+requires-python = ">=3.11"
+
+[[package]]
+name = "letzshop-product-import"
+version = "0.1.0"
+source = { editable = "." }