[project-demos]: add Sliplane deploy flow from README button

[ArtemLazarchuk]

Summary

• Add a dedicated SliplaneDeployApp reachable at /sliplane-deploy-app for one‑click deployments from GitHub README buttons.
• Capture ?repo= from the initial HTTP request and prefill the deploy form, remembering the last repository per user.
• Add a documented SVG “Host your Ivy app on Sliplane” button to the README as a copy‑paste example.

Changes

• Introduced SliplaneDeployApp that:

  • Uses Sliplane:ApiToken or OAuth session token.
  • Reads repository URL from DeployArgs or from a per‑user DeploymentDraftStore.
  • Opens the new DeployView with prefilled repo and derived service name.

• Added DeploymentDraftStore:

  • Stores last repo URL in a static concurrent dictionary keyed by user token or anonymous cookie.
  • Uses IHttpContextAccessor and a dedicated sliplane-deploy-repo-key cookie for anonymous flows.
  • Registered as scoped service in Program.cs.

• Added RepoCaptureFilter (IStartupFilter):

  • Intercepts initial GET /sliplane-deploy-app?repo=... before Ivy SPA strips query params.
  • Resolves DeploymentDraftStore from DI and saves decoded repo URL.

• Implemented DeployView:

  • Card layout aligned TopCenter with structured form:
    • Server → Project → Service name → Repository URL → Branch, then build/network/optional settings.
    • Placeholders for all fields via [Display(Prompt = ...)].
  • Async selects for projects/servers, env variables section in Expandable, and new Volumes section in Expandable:
    • Loads server volumes on server change.
    • Allows adding/removing volume mounts with a dialog.
  • On successful deploy:
    • Sends SliplaneRefreshSignal("services").
    • Navigates type‑safely to SliplaneServicesApp.

• Updated chrome configuration in Program.cs:

  • Default app set to SliplaneDeployApp.
  • Registered AddHttpContextAccessor, scoped DeploymentDraftStore, and singleton RepoCaptureFilter.

• Updated SliplaneServicesApp:

  • Added explicit id: "sliplane-services-app" for stable navigation target.

• Added SVG asset deploy-button.svg:

  • “Host your Ivy app on Sliplane” button with branded styling.

• Updated README.md:

  • Documented “Deploy button for your repo” section.
  • Included ready‑to‑use HTML snippet:

Deploy button usage

This PR adds a reusable “Host your Ivy app on Sliplane” button that can be embedded into any GitHub README.

Example:

Code:

<p align="center">
  <a href="https://YOUR-DEPLOY-APP-DOMAIN/sliplane-deploy-app?repo=https://github.com/OWNER/REPO">
    <img src="https://raw.githubusercontent.com/Ivy-Interactive/Ivy-Examples/main/project-demos/sliplane-manage/Assets/deploy-button.svg"
         alt="Host your Ivy app on Sliplane" />
  </a>
</p>