refactor: update K8s, CI, Docker, Prometheus, scripts, and FXT CLI for api rename

- K8s: rename api-gateway → api manifests, delete web-gateway, update network policies
- CI: rename compile/deploy jobs, delete web-gateway jobs
- Docker: rename service in compose files
- Prometheus: update scrape targets and alert rules
- Scripts: update binary references in build/test/cert scripts
- FXT CLI: rename api_gateway_url → api_url (with serde alias for compat)

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

scripts/enforce_coverage.sh

@@ -29,7 +29,7 @@ PRODUCTION_MODULES=(
     "config"
     "common"
     "services/trading_service"
-    "services/api_gateway"
+    "services/api"
 )
 
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