feat: python-fastapi testing rules from cotiza-api-cloud practices

- Add Patching, Concurrency Tests, and Migration print→logging sections to tests.md
- Add 2 common errors to backend.md (replace_all uniqueness, local asyncio patching)
- Add launch.json.tmpl template for uvicorn dev server
- Clean processed inbox practices

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: luiseiman

practices/inbox/2026-03-21-project-crm-session-changes.md

@@ -0,0 +1,11 @@
+{
+  "version": "0.0.1",
+  "configurations": [
+    {
+      "name": "api",
+      "runtimeExecutable": "python",
+      "runtimeArgs": ["-u", "-m", "uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8080", "--reload"],
+      "port": 8080
+    }
+  ]
+}

stacks/python-fastapi/launch.json.tmpl

@@ -30,3 +30,5 @@ Python 3.12+, FastAPI, async/await nativo. Type hints en funciones públicas. Ru
 - Olvidar `await` en async calls → retorna coroutine, no resultado
 - `response_model` sin `model_config = ConfigDict(from_attributes=True)` → falla con ORM
 - Background tasks que no capturan excepciones → mueren silenciosamente
+- `replace_all=True` in Edit without checking uniqueness — multiple similar patterns in a file get clobbered
+- Local `import asyncio` inside functions: `patch("module.asyncio.sleep")` fails with AttributeError — use `patch("asyncio.sleep")` directly

stacks/python-fastapi/rules/backend.md

@@ -16,6 +16,20 @@ globs: "tests/**/*.py"
 - Fixtures async: `@pytest_asyncio.fixture` (no `@pytest.fixture` para async)
 - httpx.AsyncClient para test de endpoints FastAPI
 
+## Patching
+- Patch targets follow the namespace where the name is **used**, not where it's **defined**. After refactoring a method to a new module, update all `patch()` paths accordingly
+- If a module uses `import asyncio` locally inside a function (not at top-level), patch `asyncio.sleep` globally — not `module.asyncio.sleep`
+- After delegating/extracting methods to new modules, search all `patch()` calls targeting the old module's internals
+
+## Concurrency Tests
+- Threads don't propagate exceptions to the main thread by default. Use a `_run_threads(target, n, *args)` helper that wraps target in try/except, collects exceptions in a shared list, and asserts empty after join
+- Verify RLock by behavior (acquire twice from same thread with `blocking=False`), not by `type().__name__` — internal type `_RLock` is private and may change
+
+## Migration print→logging
+- Replace adjacent `print(f"... {e}")` + `traceback.print_exc()` with a single `logger.exception(f"... {e}")` — it includes the full traceback
+- Remove orphaned `import traceback` after migration
+- Remove module prefix constants (e.g. `PRINT_PREFIX = "[module]"`) — logger name provides this
+
 ## Coverage
 - No apuntar a 100% — cubrir paths críticos y edge cases
 - Priorizar: happy path, error handling, boundary conditions