fix: make self-host Agent tab and dashboards work end-to-end

[venkateshsakamuri-lab]

Summary

• Route Agent tab (/agent-api) and backend dashboard generation through host Hermes on :8787 (host.docker.internal, nginx $http_host, Vite changeOrigin: false) so CSRF and Docker networking stop 502ing.
• Switch Hermes profile (cookie jar in AgentChatClient, frontend switchAgentProfile) before session create so chat/start no longer 404s under default.
• Add scripts/self-host/setup-agent.sh (+ install/smoke/status wiring, e2e check) so a fresh self-host gets MCP SDK, MCP token, and webui without manual Hermes setup; harden agent/install.sh for DEEPSQL_CHAT_* and nested HERMES_HOME.

Test plan

• ./scripts/self-host/setup-agent.sh starts webui; curl -fsS http://127.0.0.1:8787/api/mcp/servers lists deepsql
• Log in at :3000 → Agent tab boots, runs a SQL question via MCP
• Dashboards → AI generate returns an HTML artifact (no “agent unavailable” 502)
• ./scripts/self-host/smoke-test.sh passes agent path checks (profile/switch + backend session)
• Confirm Brain jobs scheduler no longer NPEs on null consecutive_failures

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