fix(deploy): give migrate the API's client-address settings, and say what Doctor checked

Doctor checks the client-address configuration of the process it runs
in, and operators run it as `migrate`. The proxy overlay set
trusted-proxy mode on `api` only, so Doctor reported "Direct
client-address mode" for an installation that trusts its proxy.

- compose.proxy.yaml defines the three variables once, as a YAML
  anchor, and applies it to both `api` and `migrate`. Rendered with
  `docker compose config`, `api` is unchanged and `migrate` now
  matches it, keeping NODE_EXTRA_CA_CERTS from the base.
- The example deploy/.env sets
  COMPOSE_FILE=compose.yaml:compose.proxy.yaml, as the instance already
  does. Plain `docker compose run --rm migrate ...` in the README then
  runs with the overlay; it used to read compose.yaml alone.
- Every client-address check in Doctor now says it checked the
  environment Doctor runs with, and how to read the running API's own
  value (`docker compose exec api printenv
  EKKLESIA_CLIENT_ADDRESS_MODE`, confirmed to work in the image).
- The deploy README explains why operator commands need the same files
  as the stack.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

core/src/diagnostics/doctor.ts

@@ -905,17 +905,25 @@ function databaseTransportCheck(
   }
 }
 
+/** Doctor reads only its own process's environment, so it says so: run as the reference
+ * deployment's `migrate`, it is given the API's values by the proxy overlay, but run any other way
+ * it may be checking a configuration the API is not running. */
+const CLIENT_ADDRESS_SCOPE =
+  "Checked: the environment Doctor runs with. In the reference deployment `migrate` is given the API's client-address values; a running API's own value is shown by `docker compose exec api printenv EKKLESIA_CLIENT_ADDRESS_MODE`.";
+
 function clientAddressCheck(input: ClientAddressConfigInput | undefined): DoctorCheck {
   try {
     const config = createClientAddressConfig(input, TRUSTED_CLIENT_ADDRESS_HEADER);
     if (config.mode === "direct") {
       return freezeCheck("identity.client-address", "pass", "Direct client-address mode", [
         "Trusts only the actual immediate socket peer for rate limiting; no forwarded header is trusted.",
+        CLIENT_ADDRESS_SCOPE,
       ]);
     }
     return freezeCheck("identity.client-address", "pass", "Trusted-proxy client-address mode", [
       `Trusts header "${config.header}" only from a request whose immediate socket peer matches one of ${config.trustedProxies.length} configured trusted ${plural(config.trustedProxies.length, "proxy")}.`,
       "The reverse proxy must overwrite (never append to) this header, and the origin must not be reachable except through it.",
+      CLIENT_ADDRESS_SCOPE,
     ]);
   } catch (error) {
     const code =
@@ -926,7 +934,7 @@ function clientAddressCheck(input: ClientAddressConfigInput | undefined): Doctor
       "identity.client-address",
       "failure",
       "Client-address configuration invalid",
-      [`[${code}] Configured client-address values failed validation.`],
+      [`[${code}] Configured client-address values failed validation.`, CLIENT_ADDRESS_SCOPE],
     );
   }
 }