fix: run pocketbase as root + add healthcheck start_period

- Remove non-root user from pocketbase Docker image; the existing pb_data
  volume was created by the previous root-running image so files are owned
  by root — running as a non-root appuser caused an immediate permission
  error and container exit
- Increase healthcheck retries to 10 and add start_period=30s so migrations
  have time to run on first boot before liveness checks begin

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -91,7 +91,8 @@ services:
       test: ["CMD", "wget", "-qO-", "http://localhost:8090/api/health"]
       interval: 10s
       timeout: 5s
-      retries: 5
+      retries: 10
+      start_period: 30s
 
   # ─── Meilisearch (full-text search) ──────────────────────────────────────────
   meilisearch: