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

server/src/storage/redis.ts

@@ -10,7 +10,7 @@ export default class RedisStorage implements StorageInterface {
     constructor() {
         const HOST = process.env.REDIS_HOST ?? 'localhost';
         const PORT = process.env.REDIS_PORT ?? 6379;
-        client = createClient({ url: `redis://${HOST}:${PORT}` });
+        client = createClient({ url: `redis://${HOST}:${PORT}` }) as RedisClientType;
     }
 
     async initialize() {
@@ -29,6 +29,39 @@ export default class RedisStorage implements StorageInterface {
 
     async setData<Type>(key: string, data: Type) {
         await client.json.set(key, '.', data as any);
-        await client.json.get(key);
     }
-}
+
+    async updateData<Type>(key: string, mutator: (current: Type | undefined) => Type): Promise<Type> {
+        return (client as any).executeIsolated(async (c: any) => {
+            for (let attempt = 0; attempt < 10; attempt++) {
+                await c.watch(key);
+                const current = await c.json.get(key, { path: '.' }) as Type | undefined;
+                const next = mutator(current);
+                const multi = c.multi();
+                multi.json.set(key, '.', next);
+                const result = await multi.exec();
+                if (result !== null) return next;
+            }
+            throw new Error(`updateData: optimistic lock failed after 10 retries for key: ${key}`);
+        });
+    }
+
+    async healthCheck(): Promise<boolean> {
+        try {
+            const pong = await client.ping();
+            return pong === 'PONG';
+        } catch {
+            return false;
+        }
+    }
+}
+
+/** Vrátí hlavní Redis klient — používá se pro lease připomínkovače a shutdown. */
+export function getRedisClient(): RedisClientType | undefined {
+    return client;
+}
+
+/** Zavře připojení k Redisu. Volá se při graceful shutdown. */
+export async function shutdownRedisStorage(): Promise<void> {
+    await client?.quit();
+}