fix: resolve 3 in-container test failures in CI compose run

1. REST 404 "Unknown host: prosody": the tester reaches prosody by
   service name (http://prosody:5280), so aiohttp sends Host: prosody,
   which Prosody rejects as an unknown vhost. The auto host-header
   heuristic only overrides for IP/localhost. Set REST_HOST_HEADER=
   example.com explicitly in the tester env so HTTP routing lands on the
   example.com VirtualHost that serves mod_http_rest /rest.

2. healthcheck.sh not found: the static test_04_infra checks resolve
   ../config/healthcheck.sh (= /config/healthcheck.sh) but the tester
   image only ships /tests. Mount ./config:/config:ro so the path
   resolves inside the container.

3. telnet non-loopback banner: read only 256 bytes, capturing just the
   ASCII-art top and never the literal "Prosody" text. Bump to 1024 to
   match test_04_infra.test_telnet_banner, which passes with the larger
   read.

Part-of: <http://gitlab.vnc.biz/uxf/vnctalk-prosody/-/merge_requests/3>

docker-compose.yml

@@ -98,8 +98,17 @@ services:
       PG_PASSWORD: prosody
       PG_DB: prosody
       MOCK_URL: http://mocks:8080    # for side-effect assertions
+      # The tester reaches prosody directly by service name (http://prosody:5280),
+      # so aiohttp sends Host: prosody — which Prosody rejects as an unknown
+      # vhost (404 "Unknown host"). Send the real XMPP domain so HTTP routing
+      # lands on the example.com VirtualHost that serves mod_http_rest /rest.
+      REST_HOST_HEADER: example.com
     volumes:
       - ./tests:/tests
+      # Surface the repo config/ dir so static tests (test_04_infra
+      # healthcheck source checks) can resolve ../config/healthcheck.sh
+      # from inside the container.
+      - ./config:/config:ro
 
 volumes:
   pgdata:

tests/test_11_smokes.py

@@ -163,7 +163,7 @@ class TestAdminTelnetNonLoopback:
             reader, writer = await asyncio.wait_for(
                 asyncio.open_connection(host, port), timeout=5
             )
-            data = await asyncio.wait_for(reader.read(256), timeout=5)
+            data = await asyncio.wait_for(reader.read(1024), timeout=5)
             writer.close()
             await writer.wait_closed()
         except (OSError, asyncio.TimeoutError) as e: