docs: explain how to reconcile snapshot totals

[kelsos]

The snapshots page covered the 1.44 totals check in a single sentence. A user who opens an old snapshot to delete a spam token finds the balances locked behind a Totals do not match warning, and the page does not say what the warning compares or how to clear it.

What changes

• Reconcile the totals (new section): what the two sums are, why they drift apart (a balance or a location edited by hand before 1.44), the steps through Absorb difference into and Reconcile locations, and the locations drawer for a difference spread over several locations. Also that Distribute across locations asks for each location's new value, not the difference, and that the preselected location has to be checked: it is the largest one (the one a spam token inflates) or the choice carried over from the previous snapshot.
• Example: remove a high-value spam token: the case that sends people here, end to end.
• Edit a snapshot: how to reveal hidden rows. An auto-ignored spam token needed both Show spam and Show ignored before its row appeared.
• Browse snapshots: why the list and the editor can show different net worths. The list and graph subtract ignored assets while the editor does not, so the same snapshot can read 60,000 in the list and 1,313,200 when opened. And a stale stored total is corrected in the editor with no warning, but only stored on the next save. Without premium the list only covers the last two weeks, so older snapshots look missing.

How it was checked

Every step was walked through on a v1.44.0 build with imported snapshots:

• two carrying a 1,250,000 USD spam token (the Cyrillic "Тether USD" lookalike), one with a location edited earlier and one with a balance edited earlier. Each was reconciled, the spam row deleted and the snapshot saved, and the stored rows were read back from the API;
• one whose balances and locations agree but whose stored total does not (63,000 against 70,000). It opens at 63,000 with no warning and Save disabled, the list keeps 70,000, and the next saved change writes 63,000.

The editor code involved is unchanged on develop since v1.44.0. lint, check:images, check:anchors, check:app-links and build pass.

Screenshots

Four new images, captured from the same v1.44.0 build at 1400x957 and 2x, lossless webp:

• reconcile_warning.webp: the summary card with the Totals do not match warning, Kraken chosen to absorb the difference.
• balances_locked.webp: the balances table locked, with Add balance disabled and the spam row counted as hidden.
• balances_filter_menu.webp: Show ignored already on, the row still hidden, Show spam offered.
• delete_balance_dialog.webp: deleting the spam token, previewing Blockchain going from 1,300,000 to 50,000.

Left out on purpose

The page describes today's behaviour. The editor's rough edges this turned up are app bugs and will be filed separately: a stale stored total is corrected on open but not marked as a change, so it cannot be saved on its own; the reconcile preselection picks the largest location and sticks across snapshots; the warning text offers to "set the total to the balances sum" with no control for it. When those are fixed, the sentences describing them here need updating.