feat: image generation workbench and provider routing (v0.18.0)

[wutongci]

Summary

• integrate installed plugin frontends with the AsterRouter console and personal navigation
• add image-generation artifact delivery, retry-safe media execution, and hosted result access
• expand Provider Account management with API-key routing, model mappings, account runtime settings, batch controls, and guarded deletion
• harden Docker deployment and add an explicit GHCR release workflow
• bump backend and frontend release sources to 0.18.0

Verification

• go test -race ./...
• go vet ./...
• npm run test:unit (35 files, 123 tests)
• npm run typecheck
• npm run build
• npm run check:enterprise-surface
• npm run check:workflow-pipefail
• npm run check:public-doc-links
• Playwright UI verification at 1440x900, 1280x800, and 390x844

Notes

• runtime data/, local test results, frontend build output, and .codex/config.toml are excluded
• local Docker acceptance was not run because no Docker daemon was available; the release workflow performs container acceptance before publishing

Documentation

• README.md: documents delivered multimodal/job/plugin capabilities, Go 1.26, and the current Docker demo variable.
• README.zh-CN.md: mirrors the same release facts in Simplified Chinese.
• deploy/DOCKER.md: documents bundled and external PostgreSQL deployment plus the manual GHCR workflow.