feat: add standards wiki, MCP registry, and app template

standards_src/wiki/02_layering_rules.md

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+# Layering Rules
+
+## Summary
+
+The dependency direction is fixed. Violating it is a design defect.
+
+---
+
+## Allowed imports
+
+```
+interfaces/*      ->  domain/*            (services, ports, models)
+interfaces/*      ->  infra/adapters/*    (only read-only value objects)
+domain/*          ->  domain/*            (same layer)
+domain/*          ->  pipelines/*         (call a pipeline via a port)
+infra/adapters/*  ->  domain/ports/*      (implement the interface)
+main.py/init.py   ->  everything          (composition root only)
+```
+
+## Forbidden imports
+
+```
+domain/*          ->  interfaces/*        (never)
+domain/*          ->  fastapi/starlette   (never)
+infra/adapters/*  ->  interfaces/*        (never)
+interfaces/*      ->  infra/db/*          (state lives in resources, not imports)
+```
+
+## Why
+
+- A pure domain is testable without a server, a database, or an event loop.
+- Adapters can be swapped (in-memory fake, real database) without touching
+  business logic.
+- The HTTP edge stays thin and replaceable.
+
+## The port/adapter contract
+
+A **port** is an abstract class or protocol declared in `domain/<x>/ports/`.
+An **adapter** implements it in `infra/adapters/`. The composition root binds
+the two.
+
+```
+domain/<resource>/ports/db.py       -> repository port + document model
+domain/<resource>/ports/service.py  -> service + factory
+infra/db/repos/<vendor>.py          -> repository adapter factory
+infra/adapters/service.py           -> generic CRUD service base
+```
+
+## Enforcement
+
+- Keep every domain module importable with only the standard library and
+  Pydantic. If a domain import pulls in `fastapi`, the layering is broken.
+- Reviewers (and CI) reject `import fastapi` inside `domain/` or `infra/`.