Scaffold FastAPI + MySQL + Keycloak service with devcontainer

Sets up the project skeleton:

- FastAPI app factory with lifespan, request-id middleware, and RFC 9457
  problem+json error handlers
- Async SQLAlchemy 2.0 over MySQL (asyncmy), with a constraint naming
  convention in place before the first migration and async Alembic
- Keycloak as a pure resource server: OIDC discovery, cached JWKS with
  rotation-aware refresh, and require_roles dependencies
- Devcontainer running MySQL 8.4 and Keycloak 26.7 as compose siblings,
  with the realm (clients, roles, test users) imported on first boot
- Test suite covering the endpoints plus the token validator itself,
  exercised against a locally generated RSA keypair
- uv packaging, ruff, mypy --strict, pre-commit, Gitea CI, prod Dockerfile

Two Keycloak-in-containers traps are handled explicitly and documented in
the README: the issuer/internal-URL split (the browser sees localhost:8080,
the API sees keycloak:8080) and the audience mapper that stops Keycloak
issuing tokens with aud=account.

The devices resource is a placeholder proving the routing -> auth -> ORM ->
migration path end to end; replace it with the real domain.

Co-Authored-By: Claude Opus 5 <[email protected]>

.devcontainer/devcontainer.json

@@ -0,0 +1,41 @@
+{
+  "name": "v2x-server",
+  "dockerComposeFile": ["../compose.yaml", "compose.override.yaml"],
+  "service": "app",
+  "workspaceFolder": "/workspaces/v2x-server",
+  "shutdownAction": "stopCompose",
+
+  "forwardPorts": [8000, 8080, 3306],
+  "portsAttributes": {
+    "8000": { "label": "API", "onAutoForward": "notify" },
+    "8080": { "label": "Keycloak", "onAutoForward": "silent" },
+    "3306": { "label": "MySQL", "onAutoForward": "silent" }
+  },
+
+  // The venv lives on a named volume owned by root until first use.
+  "postCreateCommand": "sudo chown vscode:vscode .venv && uv sync --frozen && uv run pre-commit install",
+
+  "remoteUser": "vscode",
+
+  "customizations": {
+    "vscode": {
+      "extensions": [
+        "ms-python.python",
+        "ms-python.vscode-pylance",
+        "charliermarsh.ruff",
+        "ms-python.mypy-type-checker",
+        "tamasfe.even-better-toml"
+      ],
+      "settings": {
+        "python.defaultInterpreterPath": "/workspaces/v2x-server/.venv/bin/python",
+        "python.testing.pytestEnabled": true,
+        "python.testing.pytestArgs": ["tests"],
+        "editor.formatOnSave": true,
+        "[python]": {
+          "editor.defaultFormatter": "charliermarsh.ruff",
+          "editor.codeActionsOnSave": { "source.organizeImports": "explicit" }
+        }
+      }
+    }
+  }
+}