New row at y=4 with 4 stat panels showing net-worth change over the
trailing windows. Each uses the latest-per-account stitching pattern
(skew-resilient against partial-day syncs) and computes:
delta = SUM(latest per account) - SUM(latest per account at or
before max_complete - N)
Where max_complete is the most recent date all accounts have a row.
For each window: 1d, 7d, 30d, 90d.
Verified live values: +£8,575 / +£22,696 / +£144,633 / +£174,612.
All panels at y >= 4 shifted down by 4 rows to make room (Net worth
chart 4->8, Per-account stacked 24->28, Activity log 77->81, etc.).
Note: this commit also reformats the dashboard JSON from compact-
object form to indented form (json.dump indent=2 side effect from the
Python patch script). No semantic changes outside the new panels and
y-shifts.