Implement service management API endpoints

[kanghengliu]

Parent: #247
Depends on: #248

Goal

Implement the new service management API endpoints and migrate existing tooling/documentation to use them instead of cli/service_mgmt.sh).

Tasks

• Add authenticated HTTP handlers for service CRUD, state toggles, health/monitoring, and group/scopes wiring as defined in Design HTTP parity for service_mgmt operations #248.
• Ensure FAISS metadata + scopes.yml get refreshed via API-driven jobs rather than local shell/dcoker exec steps.
• Extend cli/mcp_client.py (or new client) to wrap these endpoints for backwards compatibility.
• Update docs (docs/service-management.md, README references) and remove Bash-specific instructions.
• Add regression tests (unit + e2e) covering success/error flows.