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"
 )
 
 # Print colored message

scripts/generate_dev_certs.sh

@@ -72,7 +72,7 @@ DNS.1 = localhost
 DNS.2 = trading.foxhunt.local
 DNS.3 = backtesting.foxhunt.local
 DNS.4 = ml-training.foxhunt.local
-DNS.5 = api-gateway.foxhunt.local
+DNS.5 = api.foxhunt.local
 IP.1 = 127.0.0.1
 IP.2 = 0.0.0.0
 EOF