feat: Append to InvokeAI reference image + capability-gated recall buttons

[lstein]

Summary

Adds an "Append to InvokeAI" reference-image button to the metadata drawer, a small alignment tweak to the metadata link, and a capability probe so the recall buttons only appear when the configured InvokeAI backend actually supports them.

This is the PhotoMap side of a two-part change. It depends on a matching InvokeAI backend change (append query parameter on POST /api/v1/recall/{queue_id}); against an older backend the new button is automatically hidden by the capability probe.

What's in here (three commits)

1. fix(ui): left-align the "View Metadata (JSON)" link — both render slots (the standalone row below the recall buttons and the sticky cell at the bottom of the Image Details table) were right-aligned. Also removes a stray } in metadata-drawer.css that made the stylesheet syntactically invalid.

2. feat(invoke): "Append to InvokeAI" button — sits to the right of "Send to InvokeAI". It runs the same upload + recall flow but sends ?append=true on the recall, asking InvokeAI to add the image to its existing reference-image list instead of replacing it. New append field on UseRefImageRequest; new append_ref button mode in invoke-recall.js.

3. feat(invoke): gate the recall buttons on a backend capability probe — new GET /invokeai/capabilities probes the backend's OpenAPI schema for the recall route and its append query parameter (falling back to version thresholds — recall ≥ 6.13.0, append ≥ 6.13.5 — when the schema can't be fetched). The frontend reflects the result as body classes that CSS uses to reveal the buttons:

   • no recall router → no recall buttons at all
   • recall without append → Send to InvokeAI / Remix / Recall only
   • recall with append → all buttons

   Probing capabilities rather than comparing versions keeps a development backend working the moment the feature lands on its branch. Results are cached (5 min on success, 30 s on failure) and the cache is dropped when the InvokeAI settings are saved.

Testing

• make test green: 436 backend (pytest) + 379 frontend (Jest) tests.
• New coverage: capability tiers (OpenAPI + version fallback, unreachable, cache/refresh/invalidation), the append recall parameter, and the body-class gating.
• ruff, eslint, and prettier all clean.

🤖 Generated with Claude Code