Stage 0: scaffold monorepo, backend skeleton, docs, CI

- go.work (Go 1.26.3) with backend module; deps added incrementally (gin+zap only)

- backend: /healthz + /readyz, env config, graceful shutdown

- docs: ARCHITECTURE, FUNCTIONAL (+ru mirror), TESTING

- PLAN.md (stage tracker + per-stage open details) and CLAUDE.md (per-stage workflow)

- .gitea go-unit CI (gofmt/vet/build/test)

.claude/settings.json

@@ -0,0 +1,24 @@
+{
+  "permissions": {
+    "allow": [],
+    "defaultMode": "default"
+  },
+  "sandbox": {
+    "network": {
+      "allowedDomains": [
+        "github.com",
+        "registry.npmjs.org",
+        "*.npmjs.org",
+        "docker.com",
+        "docker.io",
+        "gcr.io",
+        "*.golang.org",
+        "gitea.iliadenisov.ru"
+      ],
+      "allowUnixSockets": [
+        "/var/run/docker.sock"
+      ],
+      "allowLocalBinding": true
+    }
+  }
+}