feat(byo): 'My stands' — bring-your-own-inventory overlay

[holoros]

What

A My stands tab that closes the biggest competitive gap (upload-your-own-inventory, vs Forest Flux / OSI) on PERSEUS's multi-model footing.

• Upload a CSV of your stand or monitoring observations: a year (or age) column and a value column, optional stand id. A tolerant parser auto-detects the columns and handles headered, headerless, and tab-delimited files.
• Your points plot over the selected state's cross-engine envelope for the current metric and management — the full engine range as a band, the ensemble median as a dashed line.
• Each stand is shaded green if it sits above the model median for its year, amber if below. Summary cards show how many stands, the share above median, and mean deviation from the median.

Why

This is the 'are the models tracking my forest?' view — it lets a landowner or analyst sanity-check their inventory against the regional model ensemble, which is exactly what Forest Flux does from USFS methods but here with the multi-model spread PERSEUS uniquely provides.

Privacy / scope

• Runs entirely client-side (FileReader); nothing is uploaded anywhere.
• One new component + 4 wiring lines in App. No data or schema change. CSV parser unit-checked across headered / headerless / age-biomass / tab inputs; npm run build passes.

Opened for review — not auto-merged.