docs: reorganize into design, security, api, ops and dev; drop stale designs; refresh the diagrams [CI]

- Group docs by category with an index (docs/README.md); fix every link,
  code comment and the protocol conformance test that read docs/protocol.md.
- access.md and security.md rewritten to what is implemented: removed the
  unadopted member-proof chain, roles and recovery key that do not exist,
  the old implementation order and the budgets; gaps now carry a status.
- enrollment, deployment, api: the install flow is the static, hash-checked
  script with environment variables; no default admin.
- README and architecture: new topology and update-flow diagrams (operator
  passkey, CI signing, registry feed, auth and trust modules).

backend/tests/MoShiro.Backend.Tests/QueryPlanningTests.cs

@@ -6,7 +6,7 @@ using MoShiro.Protocol;
 
 namespace MoShiro.Backend.Tests;
 
-/// <summary>时间段、步长与数据源的规划：与 docs/query.md 里的表格逐行对应。</summary>
+/// <summary>时间段、步长与数据源的规划：与 docs/design/query.md 里的表格逐行对应。</summary>
 public sealed class QueryPlanningTests
 {
     private const long Second = 1000;