feat(config): add readyOnStart option to dynamic strategy

[ngoc-minh-do]

What

Adds ready_on_start query parameter to the dynamic strategy. When true, Sablier returns X-Sablier-Session-Status: ready immediately regardless of instance health — the reverse proxy passes the request through without showing a waiting page.

The per-instance sablier.ready-on-start label controls behavior per container. The query param does the same, but at the middleware level — no labels needed.

Why

Sometimes you want different behavior depending on which service is accessed:

Home Assistant + Frigate: When loading the HA dashboard, you want Frigate to start in the background — no need to wait. But when accessing Frigate's own UI directly, you want the waiting screen to confirm it's ready.
Chat app + LiteLLM proxy: When users open the chat, LiteLLM starts alongside without blocking. Direct access to LiteLLM UI get the waiting screen.

Usage

GET /api/strategies/dynamic?group=myapp&ready_on_start=true

Plugin-side config (separate PRs):

    frigate-sablier:
      plugin:
        sablier:
          names: frigate
          dynamic:
            displayName: Frigate

    frigate-sablier-force:
      plugin:
        sablier:
          names: frigate
          dynamic:
            displayName: Frigate
            readyOnStart: true