feat: podpora high-availability a multi-replica nasazení

- Socket.io Redis adapter pro sdílený stav přes repliky
- graceful shutdown serveru
- WATCH/MULTI v updateData pro race-condition-safe aktualizace
- lease mechanismus pro push reminder (zabrání duplicitnímu odesílání)
- k8s/ manifesty pro testovací kind cluster
- Dockerfile: opraven EXPOSE port na 3001
- .gitignore: ignorovány Claude pracovní soubory

.vscode/launch.json

@@ -0,0 +1,32 @@
+{
+  "version": "0.2.0",
+  "configurations": [
+    {
+      "name": "Server (ts-node, debug)",
+      "type": "node",
+      "request": "launch",
+      "cwd": "${workspaceFolder}/server",
+      "runtimeArgs": ["-r", "ts-node/register"],
+      "program": "${workspaceFolder}/server/src/index.ts",
+      "env": { "NODE_ENV": "development" },
+      "console": "integratedTerminal",
+      "skipFiles": ["<node_internals>/**"],
+      "preLaunchTask": "types: openapi-ts"
+    },
+    {
+      "name": "Client (vite + Edge)",
+      "type": "msedge",
+      "request": "launch",
+      "url": "http://localhost:3000",
+      "webRoot": "${workspaceFolder}/client",
+      "preLaunchTask": "client: vite"
+    }
+  ],
+  "compounds": [
+    {
+      "name": "Dev: server + client",
+      "configurations": ["Server (ts-node, debug)", "Client (vite + Edge)"],
+      "stopAll": true
+    }
+  ]
+}