Refactor navigation pins and interaction surfaces

[dovvnloading]

Summary

• refactor navigation pins around a validated, Qt-free record store and controller
• replace the legacy pin overlay/list rebuild path with a model-driven in-window panel and shared editor
• harden pin graphics geometry, drag persistence, context actions, stable IDs, ordering, and database migration
• keep navigation pins out of Fit All by default and route creation/edit/delete/focus through one scene boundary
• preserve the neutral grayscale UI work and generated composer assets already included in the local update

Root cause

Navigation pins previously had multiple mutable sources of truth, a window-coupled overlay, duplicated editor code, prototype-level graphics geometry, and persistence without stable identifiers or deterministic ordering. That combination caused stale panel state, repaint trails, fragile deletion paths, and migration risk.

Validation

• python -m pytest -q --basetemp .pytest-tmp — 475 passed
• Qt runtime smoke test for the pin panel, store-backed model, and literal filtering passed
• targeted Python compilation passed
• git diff --check passed

The local-only doc/ proposal remains intentionally excluded from this public repository.