robustness: split jetstream into own container, add cursor persistence

Jetstream was running backgrounded in the same container as the API server,
so crashes went undetected and Docker never restarted it. Now each process
runs as a separate docker-compose service with independent restart policies.

Also adds cursor persistence to SQLite (saved every 5s) so restarts resume
from where they left off, moves event destructuring inside try/catch blocks,
and adds global unhandled error/rejection handlers for crash visibility.

docker-compose.yml

@@ -1,8 +1,17 @@
 services:
-  api:
-    # build: .
+  jetstream:
     image: docker.li212.fr/litenote:latest
     restart: unless-stopped
+    command: ["sh", "-c", "deno task migrate && deno task jetstream:prod"]
+    env_file:
+      - .env
+    volumes:
+      - ${DATA_VOLUME:-data}:/data
+
+  api:
+    image: docker.li212.fr/litenote:latest
+    restart: unless-stopped
+    command: ["deno", "task", "server:prod"]
     ports:
       - "${PORT}:8080"
     env_file: