Fix autopilot schedule preview version mismatch (ZIC-121)

[vicksiyi]

What does this PR do?

Fixes the autopilot schedule editor's error mapping when a newer web frontend talks to an older backend that does not have GET /api/autopilots/cron-preview.

Older backends can route cron-preview as /api/autopilots/{id} and return 400 {"error":"invalid autopilot id"}. The editor previously treated that 400 as a cron rejection, so valid cron like 0 10 * * * could be shown as invalid. This PR detects unsupported preview endpoints separately, keeps the schedule submittable, and shows localized self-host/backend-version guidance instead of a cron error.

Related Issue

Closes #5865

Multica issue: ZIC-121

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Refactor / code improvement (no behavior change)
• Tests (adding or improving test coverage)
• Documentation update
• CI / infrastructure

Changes Made

• Added isCronPreviewUnsupported classification for missing/unsupported preview routes, including the legacy invalid autopilot id 400.
• Updated the schedule editor to exclude unsupported preview failures from cron validation and render backend-version mismatch copy.
• Added localized unsupported-preview messages for EN, zh-Hans, JA, and KO.
• Added focused regressions for both the submit gate and rendered editor state.

How to Test

1. Open the schedule editor against an older backend that lacks GET /api/autopilots/cron-preview.
2. Enter 0 10 * * * with Asia/Shanghai.
3. Confirm the editor shows backend preview support guidance, does not mark the cron invalid, and does not disable save because of the preview route mismatch.

Local validation:

• pnpm --filter @multica/views exec vitest run autopilots/components/schedule-editor/validate.test.ts
• pnpm --filter @multica/views exec vitest run autopilots/components/schedule-editor/schedule-editor.test.tsx
• pnpm --filter @multica/views typecheck
• pnpm --filter @multica/views lint (passes with existing warnings outside this change)
• make check-worktree was attempted, but the local Docker daemon was unavailable while the target checked PostgreSQL, so the full worktree pipeline did not progress past DB setup.

Checklist

• I have included a thinking path that traces from project context to this change
• I have run tests locally and they pass
• I have added or updated tests where applicable
• If this change affects the UI, I have included before/after screenshots
• I have updated relevant documentation to reflect my changes
• If I added a new runtime / coding tool / UI tab, I synced the change to landing copy (apps/web/features/landing/i18n/) and relevant docs (apps/docs/content/docs/)
• If this PR touches Chinese product copy, I checked it against apps/docs/content/docs/developers/conventions.zh.mdx (terminology, mixed-rule for task / issue / skill)
• I have considered and documented any risks above
• I will address all reviewer comments before requesting merge

AI Disclosure

AI tool used: Multica Agent

Prompt / approach:
Traced the schedule editor preview query and submit gate, reproduced the mismatch via targeted mocked ApiError responses, then added the smallest UI-side classification and localized message changes with focused Vitest coverage.

Screenshots (optional)

Not included. This change is copy/error-state handling covered by component tests; no local backend with the old route shape was available for a live before/after screenshot.

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