fix: preserve PostgREST RPC path through DWH proxy

scripts/test-dwh-auth-nginx-integration.sh

@@ -486,7 +486,7 @@ probe_body="$temp_root/probe.body"
 expect_status verifier_not_public 404 "$probe_body" 'http://synthetic/_check_dwh_key'
 report_pass verifier_not_public
 
-route_url='http://synthetic/dwh/?keep=exact&second=two'
+route_url='http://synthetic/dwh/rpc/ping?x=keep&second=two'
 expect_status valid_v1 200 "$probe_body" \
   -H "X-API-Key: $v1_key" \
   -H 'Cookie: synthetic-session=one' \
@@ -496,7 +496,7 @@ expect_status valid_v1 200 "$probe_body" \
 [[ $(<"$probe_body") == 'postgrest-marker' ]] || fail_case valid_v1
 report_pass valid_v1
 
-expect_status valid_legacy 200 "$probe_body" -H "X-API-Key: $legacy_key" 'http://synthetic/dwh/?legacy=one'
+expect_status valid_legacy 200 "$probe_body" -H "X-API-Key: $legacy_key" 'http://synthetic/dwh/rpc/ping?legacy=one'
 [[ $(<"$probe_body") == 'postgrest-marker' ]] || fail_case valid_legacy
 report_pass valid_legacy
 
@@ -554,12 +554,12 @@ assert len(marker) == 2
 assert marker[0] == {
     "has_api_key": False,
     "has_dwh_key_id": False,
-    "path": "/dwh/?keep=exact&second=two",
+    "path": "/rpc/ping?x=keep&second=two",
 }
 assert marker[1] == {
     "has_api_key": False,
     "has_dwh_key_id": False,
-    "path": "/dwh/?legacy=one",
+    "path": "/rpc/ping?legacy=one",
 }
 PY
 report_pass header_and_path_isolation