Add authentication: admin/agent bearer tokens for the API, login for the dashboard

control-api: every route now carries a mandatory access level (admin / agent /
open) in a route table. All /api/v1/admin/* require the admin token; the
write calls of validator-agent and prober (self-check, events, results,
complete) require a separate static agent token; register, heartbeat and
fetching the assignment stay open. Tokens come from env vars, are compared in
constant time and never logged. An empty token leaves that level open with a
startup warning (backward compatible).

validator-agent / prober: apiclient sends the agent token only to control-api.

admin-dashboard: login/password (from env) with a stateless HMAC session
cookie, Origin-based CSRF check, per-IP brute-force throttle, HX-Redirect for
htmx polls, logout in the sidebar; the dashboard calls control-api with the
admin token. Login page layout fixed after review.

Also: env plumbing in docker-compose/rxprod-compose/systemd/config examples,
e2e script with token assertions, tests, docs (API, SETUP, USAGE, DASHBOARD,
README), plan and review under docs/changes/, bin/ rebuilt with new
SHA256SUMS.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

deploy/docker/control-api/control-api.docker.example.yaml

@@ -17,6 +17,13 @@ database:
 openstack:
   mode: "mock"
 
+# Статические bearer-токены читаются из переменных окружения контейнера с
+# этими именами (задаются в .env, см. deploy/docker/.env.example). Пусто =
+# соответствующий уровень API открыт (с предупреждением в логе).
+auth:
+  admin_token_env: "CONTROL_API_ADMIN_TOKEN"   # защищает /api/v1/admin/*
+  agent_token_env: "CONTROL_API_AGENT_TOKEN"   # защищает запись результатов агентами/пробером
+
 orchestrator:
   poll_interval_seconds: 5
   self_check_timeout_seconds: 60