feat: init mlkem project with Verilator test framework

- sync_rtl/common/: skid_buffer, pipeline_reg, defines (valid/ready)
- sync_rtl/mod_add/: modular adder example with Verilator C++ TB
- test_framework/: Python-driven Verilator compile/sim/compare pipeline
- test_framework/modules/mod_add/: 50-vector test plan, full鏈路 PASS
- .trellis/spec/: RTL and test_framework conventions documented

.trellis/spec/backend/database-guidelines.md

@@ -0,0 +1,51 @@
+# Database Guidelines
+
+> Database patterns and conventions for this project.
+
+---
+
+## Overview
+
+<!--
+Document your project's database conventions here.
+
+Questions to answer:
+- What ORM/query library do you use?
+- How are migrations managed?
+- What are the naming conventions for tables/columns?
+- How do you handle transactions?
+-->
+
+(To be filled by the team)
+
+---
+
+## Query Patterns
+
+<!-- How should queries be written? Batch operations? -->
+
+(To be filled by the team)
+
+---
+
+## Migrations
+
+<!-- How to create and run migrations -->
+
+(To be filled by the team)
+
+---
+
+## Naming Conventions
+
+<!-- Table names, column names, index names -->
+
+(To be filled by the team)
+
+---
+
+## Common Mistakes
+
+<!-- Database-related mistakes your team has made -->
+
+(To be filled by the team)