Name NLB uploads, delete statements, and stop importing on upload

Four changes to statement handling in the web app, made together and
touching the same upload and statements-list code.

Name NLB uploads by statement date. parser.Namer is an optional
interface, like Warner, through which a parser names its statements;
nlb reads the "Datum izpiska" from the izpisek header and names it
izpisek_YYYY_MM_DD, lowercase, extension included -- ported from the
rename_izpiski.py it replaces. Uploads are staged as dotfiles, invisible
to import, so the parser can read them; two downloads of one statement
then meet under one name and the second is recognised as already there,
while a different statement of the same date is numbered _2 as the
script did. Only uploads are named: source_files records statements by
path, so renaming a file already in a folder would orphan its rows.

Delete a statement from the statements list. The file is removed from
disk for good -- the page says so before it asks -- and
store.ForgetSourceFile drops its transactions and their transfer rows.
A row two overlapping statements share is stored once, under the file
imported first, so it goes too; the account's other statements forget
their checksums and show as changed until the next Import re-reads them
and restores it. A file already gone from disk can be forgotten.

Upload and delete no longer import. Importing stays the user's call,
made with the Import button, so a batch can be put together and looked
over first. Delete still re-pairs transfers, which reads no statement.

Show rows and new rows per statement. The list read "0" for a file
whose rows an earlier, overlapping statement already held, which looked
like a file that failed to parse. source_files now records how many
transactions each statement holds, and the list reads "3 rows · 0 new".

This adds a column the code reads, so an index built by an earlier
version fails with "no such column: s.rows": delete index.db and import
again.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/parser/nlb.go

@@ -43,6 +43,10 @@ var (
 	nlbAccount = regexp.MustCompile(`^SI\d{2}(?:\s?\d{4}){3}\s?\d{3}$`)
 )
 
+// nlbStatementDate is the issue date in an izpisek's header. It names the
+// statement: NLB's downloads are not named for what they hold.
+var nlbStatementDate = regexp.MustCompile(`Datum izpiska\s+(\d{2})\.(\d{2})\.(\d{4})`)
+
 // nlbMinContinuationIndent is the shallowest indent a wrapped description line
 // may have. The real threshold is the description column of the transaction
 // the line belongs to, measured per line rather than hardcoded: pdftotext
@@ -61,6 +65,24 @@ func (p *nlbParser) Parse(path string, acc *config.Account) ([]RawTxn, error) {
 	return parseNLBText(text, p.digits)
 }
 
+// StatementName names an izpisek after its statement date, izpisek_YYYY_MM_DD,
+// so the folder sorts by date and two downloads of one statement collide.
+func (p *nlbParser) StatementName(path string) (string, error) {
+	text, err := pdfToText(path)
+	if err != nil {
+		return "", err
+	}
+	return nlbStatementName(text), nil
+}
+
+func nlbStatementName(text string) string {
+	m := nlbStatementDate.FindStringSubmatch(text)
+	if m == nil {
+		return ""
+	}
+	return fmt.Sprintf("izpisek_%s_%s_%s", m[3], m[2], m[1])
+}
+
 // parseNLBText holds the whole parser, separated from PDF extraction so it can
 // be tested against captured pdftotext output.
 func parseNLBText(text string, digits int) ([]RawTxn, error) {