feat: configure host-specific plugin services

[sylarhcn]

Summary

• add explicit host-provided pluginServices configuration and derived capability reporting
• remove runtime CCW/Xiguacity URL hardcoding from block sharing, Piskel, custom extension versions, custom CSS, Code Find, Inspiro, and voice cooperation
• keep block-sharing's local SVG export/copy/paste/file-drop import available when remote content is unavailable
• fail closed for fully remote plugins instead of guessing Cocrea sibling domains

Cocrea behavior

• configure only the currently verified Inspiro API and asset routes
• keep Piskel, the custom extension marketplace, and voice cooperation unavailable without verified Cocrea services
• preserve local custom CSS themes and user-entered URLs while removing the CCW default example
• remove the site-owned Code Find empty-state image

Host integration contract

• gandi-gui should pass a pluginServices prop through usePluginsContext
• hub-international should pass the documented Cocrea profile
• keep Inspiro explicitly unavailable until a signed-in generation smoke test passes; keep voice cooperation unavailable
• full CCW/Cocrea profiles and capability semantics are documented in docs/host-plugin-services.md

Validation

• pnpm test:plugin-services — 6/6 passed
• pnpm build --no-stats — passed
• targeted ESLint for the routing/service changes — passed
• git diff --check — passed
• production bundle scan found none of the removed runtime service URLs
• full-repository lint remains at the existing baseline: 560 errors / 200 warnings

Not included

• no npm publication
• no changes to gandi-gui, hub-international, or Cocrea repositories