Dashboard-native edit mode: EDIT button toggles in-place editing; the
add-position form has on-blur ticker validation against a new paid
endpoint, qty input, and an avg-cost / bought-on-date toggle. Only
avg_cost + qty are persisted to localStorage (no acquisition date,
no server-side holdings). Empty state replaces "Import a CSV" with
the inline form so brand-new users can act without leaving the page.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
