fix: db/cache/store providers must serve their port; drop baserow's empty redis contribution

The breadth install (catalogue-broad) surfaced two latent resolution bugs that
single-module compile checks never caught (compile != resolve):

1. postgres/redis/mongodb/minio served no "port", yet seven consumers
   (baserow, letta, invoicing, gitea, umami, keycloak, nextcloud) reference
   ${bound:<provision>:port}. A binding auto-carries at/from/as; the port is the
   provider's half of the answer and must be declared in `serves` (manifest.go:
   "Serves is what a consumer needs to know ... a port, a path, a realm"). Added
   port to each: postgres 5432, redis 6379, mongodb 27017, minio 9000. Without it
   no DB consumer could resolve, let alone deploy.

2. baserow declared an empty contribution `contributes: {"redis-cache": {}}`.
   redis's serves spec for the cache is empty (a cache takes no per-consumer
   payload), so a consumer only `requires` it; an empty contribution is refused.
   Dropped it (requires/binds/secrets unchanged).

Found by mesh-lab catalogue-broad; the same fixes are mirrored in that bed.

Claude-Session: https://claude.ai/code/session_01LrgweAeERJYBg88c5cKDzF

modules/postgres/module.json

@@ -27,7 +27,9 @@
     }
   ],
   "serves": {
-    "postgres-database": {}
+    "postgres-database": {
+      "port": 5432
+    }
   },
   "receives": {
     "postgres-database": "/var/lib/postgres/grants/mesh.json"