v0.4.0

Prompt Pool release.

Added:

• Prompt Pool route with masonry browsing, search, media/model filters, readiness sorting, and detail previews.
• Prompt favorites with local groups, bookmark actions, copy/use flows, usage metadata, and a floating canvas quick-access panel.
• Bundled Prompt Pool API/data support with PROMPT_POOL_DIR override and Docker image inclusion.

Changed:

• Canvas navigation now includes Prompt Pool.
• Prompt Pool browsing auto-loads near scroll end and favorite prompts use a viewport-aware tooltip.
• Bundled Prompt Pool data refreshed to 2,968 prompts and 5,365 referenced assets.