One JSON document for storage; read-only dashboard; import asks before wiping

[Grantmiller99]

Follow-up to #1, #2 and #4. Rebuilds the storage layer around a single JSON document, makes the dashboard a read-only view, and gives import a choice instead of always destroying what you have. The format is documented in DATA.md.

1. Import asks whether to wipe your entries

Import always replaced everything, so restoring a backup silently destroyed any entries added since it was taken. It now asks.

The file is parsed and validated before anything is stored, so the dialog shows real numbers — "This file holds 12 entries. You currently have 4 stored." — and an unusable file can never damage what is already there.

Answer	Effect
Yes — wipe and replace	Discard everything stored, entries and settings, keeping only the backup. The old behaviour, now chosen deliberately.
No — keep mine and add	Append the file's entries to what is stored. Existing entries and existing settings are left alone.
Cancel	Nothing is touched. Backdrop click and Escape do the same.

With nothing stored yet there is nothing to wipe, so the question is skipped and the file imports directly.

On add, an entry already present (same id — what happens when the same file is imported twice) is counted as a duplicate and skipped rather than added again.

Native confirm() only offers two answers, so this is a small in-page dialog styled to match the settings panels. Every outcome reports what actually happened: entries added or restored, duplicates skipped, entries dropped for a bad date or amount, and how many of your own entries were wiped.

2. Storage is one JSON document

All data lives in one document under one key — think of it as a single JSON file. Every operation reads or writes the whole thing, so nothing writes a partial record.

Call	What it does
read()	Parse the document. Corrupt data returns an empty one instead of breaking the page.
write(doc)	Serialise the whole document back over the key.
clear()	Delete the key outright. A later read does not recreate it, so cleared stays cleared.
parseBackup(text)	Validate a backup without storing it.
replaceWith(doc) / mergeWith(doc)	Wipe, or keep and add.
exportToFile()	Write the document out verbatim.

Export re-imported with wipe returns identical data, ids included. One validateEntry gate covers both typed input and imported files, so a form and a backup cannot disagree about what a valid entry is.

3. Dashboard is a read-only view

"Incoming Paychecks" and "Weekly Spending" mirror the Entries page — same Date / Amount / Notes columns, same newest-first order — with no add forms and no delete buttons. Each panel links to Entries for editing, so entries are managed in exactly one place. Both listings now show every entry, scrolling inside the panel with a sticky header, rather than silently cutting off after five rows.

Totals, charts and listings all refresh from the stored document, so entries added on Entries or Groceries and data restored by an import both land on the dashboard correctly.

Verified

Driven through the real UI against a local server, no console errors:

Check	Result
Dialog contents	"This file holds 2 entries. You currently have 2 stored." + three buttons
Cancel / Escape / backdrop	Dialog closed, entries untouched
No — keep and add	"Added 2 entries to your existing ones — 4 total. Your settings were kept." Own settings (35%) survived the file's 40%
Same file added twice	"Added 0 entries… 2 entries were already present and skipped." Total stayed 4
Yes — wipe and replace	"1 entry restored… Your previous 2 entries were wiped." File's settings (40%) applied
Empty store	No question asked; imported directly, no misleading "wiped" line
Invalid file	Rejected before anything was stored
Clear	Key is null; a later read does not recreate it
Add on Entries page	Dashboard totals, listing and charts updated live in another tab
Export → clear → import	Entries, settings and ids identical
Dashboard read-only	0 forms, 0 inputs, 0 delete buttons, 2 "Manage on Entries" links