Set up sandboxes page by page

[SaladDay]

Feedback: "这个界面还是有点太复杂了，我觉得可以做成onboarding那种一页一页的翻页效果…每个页面让用户选择的可以少一点（但是高级设置还是要在…）沙箱运行后端这里你也可以用一个问号给他们讲明白docker和microsandbox有啥区别", and "你就得在系统那儿把 sandbox 的规格也写上去吧". Builds on the #95 deployment contract.

• Sandbox setup as pages (SandboxSetupWizard, replaces SandboxSetup): where sandboxes run → Docker or microsandbox (the difference is behind a help tip) or the E2B account → the size of each sandbox (small / standard / large) → review. Large choice cards advance on a click; pages slide across; progress dashes on top. Advanced settings, one link away, hold the complete form (resources and disks, Core address, the six Runtime release fields, E2B template).
• Deployment writes now send resources and runtime, which Unify deployment sandbox configuration and node specifications #95 requires. Docker and microsandbox omit disks; microsandbox sends root and environment disks. For Docker and microsandbox, the Runtime release comes from the console's own /node-install/manifest.json through Unify Core process configuration and administrator-approved node capacity #107's distributionRuntime. Without a manifest, the release is entered under advanced settings.
• The review asks for the Core address only when the console's own address can't be used (loopback or plain HTTP).
• Changing the provider or resources in maintenance (Unify Core process configuration and administrator-approved node capacity #107) goes through the same pages, starting with the current choices selected. The same backend keeps its saved size and Runtime; a saved size outside the presets is offered as "Current". Another backend starts from its standard size (Unify Core process configuration and administrator-approved node capacity #107's defaultSandboxResources) and this console's Runtime (distributionRuntime). E2B always needs its key again, because Core keeps no key across a change. This replaces Unify Core process configuration and administrator-approved node capacity #107's form and carries its acceptance test over to the pages.
• The E2B template check now matches Core: a template ID of up to 128 characters and a canonical, non-nil lowercase build UUID.
• The Nodes summary and System now show each sandbox's CPU, memory and disks, plus the Runtime commit.

Validation: typecheck, 330 web unit tests, 13 browser acceptance tests on headless Chromium. New: own-machine setup page by page with the Runtime from the distribution. Rewritten from #107: the same backend keeps its size and Runtime, and another backend starts from its defaults (including E2B, which needs its key again).. Gate and CI results are in the checks.