feat(pitch-deck): full pitch versioning with git-style history (#4)

Full pitch versioning: 12 data tables versioned as JSONB snapshots,
git-style parent chain (draft→commit→fork), per-investor assignment,
side-by-side diff engine, version-aware /api/data + /api/financial-model.

Bug fixes: FM editor [object Object] for JSONB arrays, admin scroll.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pitch-deck/app/pitch-admin/(authed)/financial-model/[scenarioId]/page.tsx

@@ -130,7 +130,7 @@ export default function EditScenarioPage() {
                 const isEdited = edits[a.id] !== undefined
                 const currentValue = isEdited
                   ? edits[a.id]
-                  : a.value_type === 'timeseries'
+                  : typeof a.value === 'object'
                     ? JSON.stringify(a.value)
                     : String(a.value)