feat(delivery): docker sandbox adapter + owner-only infrastructure (v2 phase A3-1)

The execution boundary for v2. Adds the local docker/podman sandbox adapter
and the hardened host subprocess runner every other delivery adapter will use.

- adapters/process.py: the one place the platform shells out. argv-only (no
  shell), start_new_session + killpg on timeout, concurrent stdout/stderr
  drains with a byte cap, explicit minimal env (never os.environ), and a
  missing binary reported as spawn_failed rather than an exception.
- adapters/docker_sandbox.py: DockerSandboxAdapter over SandboxProviderPort.
  --user 1000:1000, --cap-drop ALL, no-new-privileges, pids/cpu/memory limits,
  --read-only with tmpfs scratch, one bind mount (the work tree, never the git
  dir), labels, no published ports. Path-safe file access; secrets refused in
  `docker exec -e`. Extras for later phases: start_demo_container (loopback
  publish only), list_managed_containers, remove_container.
- registry: SANDBOX_PROVIDER=docker, cached singleton so the workspace registry
  survives create_workspace -> start_session.
- sandbox_gateway worker: reap_orphans() removes labelled containers no live
  session points at, audited as sandbox.reap; run_pass() does both passes.
- sandbox router: every mutating route now requires the platform owner
  (PLAN-v2 §7.7); read-only status routes stay open to org members.
- sandbox-panel: canManageInfra prop (fails closed) hides the create form,
  the session panel and the action buttons from non-owners.

Tests: 346 API (+37), 67 web (+3); ruff, mypy, tsc and lint clean.
Three existing tests now drive the sandbox as the platform owner, since that
is who may touch it.

Report: docs/plan/reports/agent-3-phase-1.md

apps/api/tests/test_workers.py

@@ -21,6 +21,7 @@ import pytest_asyncio
 from httpx import AsyncClient
 
 from app.domain.base import utcnow
+from app.domain.identity.models import PlatformRole
 from app.workers import base as worker_base
 from app.workers.ai_runtime import AiRuntimeWorker
 from app.workers.billing import BillingWorker
@@ -48,9 +49,18 @@ async def _workers_use_the_test_database(monkeypatch, session_factory):
     return session_factory
 
 
-async def _make_org_with_employee(client: AsyncClient, email: str) -> tuple[str, dict, str, str]:
-    """Return ``(org_id, headers, project_id, employee_id)`` for a fresh tenant."""
-    token = (await signup(client, email))["access_token"]
+async def _make_org_with_employee(
+    client: AsyncClient,
+    email: str,
+    *,
+    platform_role: PlatformRole = PlatformRole.MANAGER,
+) -> tuple[str, dict, str, str]:
+    """Return ``(org_id, headers, project_id, employee_id)`` for a fresh tenant.
+
+    ``platform_role`` is a parameter because the sandbox-gateway tests drive
+    container endpoints, which v2 restricts to the platform owner.
+    """
+    token = (await signup(client, email, platform_role=platform_role))["access_token"]
     headers = auth_header(token)
     org_id = (
         await client.post("/api/organizations", json={"name": "سازمان کارگر"}, headers=headers)
@@ -249,7 +259,7 @@ async def test_billing_roll_up_refuses_a_nonsense_period(delta: timedelta):
 async def test_sandbox_gateway_stops_an_idle_session_and_audits_it(client: AsyncClient):
     """An abandoned session must be stopped, and the stop must be auditable."""
     org_id, headers, project_id, _ = await _make_org_with_employee(
-        client, "worker-gateway@example.com"
+        client, "worker-gateway@example.com", platform_role=PlatformRole.OWNER
     )
     template_id = (
         await client.get(f"/api/organizations/{org_id}/sandbox/templates", headers=headers)
@@ -301,7 +311,7 @@ async def test_sandbox_gateway_stops_an_idle_session_and_audits_it(client: Async
 async def test_sandbox_gateway_leaves_a_fresh_session_alone(client: AsyncClient):
     """A session that was just used must not be reaped."""
     org_id, headers, project_id, _ = await _make_org_with_employee(
-        client, "worker-gateway-fresh@example.com"
+        client, "worker-gateway-fresh@example.com", platform_role=PlatformRole.OWNER
     )
     template_id = (
         await client.get(f"/api/organizations/{org_id}/sandbox/templates", headers=headers)