Add money: statement-driven personal finance tracker

A data directory holds one folder per account. Statements dropped into
those folders are parsed into a rebuildable SQLite index, categorised by
ordered glob rules in rules.toml, and browsed or hand-tagged in a Bubble
Tea TUI. Movements between the user's own accounts are marked as
transfers by the same rules and excluded from spending totals.

Manual tags and transfer marks are stored separately from the rule-derived
ones and always win, so editing rules.toml and re-running retag never
destroys hand edits.

Parsers are pluggable. Three are ported from the Python extractors they
replace -- nlb and traderepublic read PDFs via pdftotext -layout, revolut
reads the CSV export -- alongside a configurable-column CSV parser and a
cmd parser that shells out to an external script.

Both ports fix two latent bugs in the originals: the sign character class
rejected the typographic minus U+2212 that some PDF fonts emit, and NLB's
hardcoded continuation indent broke when pdftotext compressed runs of
spaces, so the threshold is now measured from the description column.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

internal/parser/amount.go

@@ -0,0 +1,109 @@
+package parser
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+// ParseAmount converts a decimal string from a statement into signed minor
+// units. It is deliberately forgiving, because statements are messy:
+//
+//	"1.234,56" (decimal ",", thousands ".")  -> 123456
+//	"-45.20"                                 -> -4520
+//	"45,20-"    (trailing minus)             -> -4520
+//	"(45.20)"   (accounting negative)        -> -4520
+//	"1 234.56 EUR"                           -> 123456
+//
+// decimal defaults to "."; every other separator is discarded, so thousands is
+// only a readability hint in account.toml and needs no special handling here.
+// digits is the account's minor-unit scale; extra fraction digits are rounded
+// half away from zero.
+func ParseAmount(s, decimal, thousands string, digits int) (int64, error) {
+	_ = thousands // dropped along with all other non-decimal separators
+	orig := s
+	if decimal == "" {
+		decimal = "."
+	}
+
+	s = strings.TrimSpace(s)
+	if s == "" {
+		return 0, fmt.Errorf("empty amount")
+	}
+
+	neg := false
+	if strings.HasPrefix(s, "(") && strings.HasSuffix(s, ")") {
+		neg = true
+		s = strings.TrimSuffix(strings.TrimPrefix(s, "("), ")")
+	}
+	if strings.HasSuffix(s, "-") {
+		neg = true
+		s = strings.TrimSuffix(s, "-")
+	}
+
+	// Keep only digits and the decimal separator. Everything else -- currency
+	// codes, symbols, thin and non-breaking spaces, thousands separators --
+	// is noise. A minus anywhere flips the sign; a plus is ignored.
+	var b strings.Builder
+	for _, r := range s {
+		switch {
+		case r >= '0' && r <= '9':
+			b.WriteRune(r)
+		case r == '-' || r == '−':
+			neg = !neg
+		case string(r) == decimal:
+			b.WriteRune('.')
+		}
+	}
+	clean := b.String()
+	if clean == "" || clean == "." {
+		return 0, fmt.Errorf("cannot parse amount %q", orig)
+	}
+
+	intPart, fracPart, _ := strings.Cut(clean, ".")
+	if strings.Contains(fracPart, ".") {
+		return 0, fmt.Errorf("cannot parse amount %q: multiple decimal separators", orig)
+	}
+	if intPart == "" {
+		intPart = "0"
+	}
+
+	whole, err := strconv.ParseInt(intPart, 10, 64)
+	if err != nil {
+		return 0, fmt.Errorf("cannot parse amount %q: %w", orig, err)
+	}
+
+	scale := int64(1)
+	for range digits {
+		scale *= 10
+	}
+
+	var frac int64
+	if digits > 0 {
+		switch {
+		case len(fracPart) > digits:
+			// Round half away from zero on the first dropped digit.
+			kept, err := strconv.ParseInt(fracPart[:digits], 10, 64)
+			if err != nil {
+				return 0, fmt.Errorf("cannot parse amount %q: %w", orig, err)
+			}
+			frac = kept
+			if fracPart[digits] >= '5' {
+				frac++
+			}
+		case fracPart != "":
+			padded := fracPart + strings.Repeat("0", digits-len(fracPart))
+			if frac, err = strconv.ParseInt(padded, 10, 64); err != nil {
+				return 0, fmt.Errorf("cannot parse amount %q: %w", orig, err)
+			}
+		}
+	} else if fracPart != "" && fracPart[0] >= '5' {
+		whole++
+	}
+
+	v := whole*scale + frac
+	if neg {
+		v = -v
+	}
+	return v, nil
+}