refactor: move Python implementation to legacy/, make Go primary

Go (go/) becomes the primary implementation. The original Python
version moves to legacy/ and is kept runnable; new features are still
built in both (see the Dual implementation rule in CLAUDE.md).

- git mv app.py, scripts/, templates/, tests/, pyproject.toml, uv.lock
  and build/ into legacy/
- Makefile: Python targets point at legacy/, venv in legacy/.venv,
  CREDENTIALS_PATH exported for the root .secret/ file
- CI and make image build the Python image with legacy/ as context;
  the Makefile is no longer copied into the image
- legacy/.dockerignore moved to the context root so it takes effect
- CLAUDE.md, docs/README.md, Go comments, fixture README, capture
  script and VS Code launch config updated to the new layout

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

go/internal/domain/matching/doc.go

@@ -1,2 +1,2 @@
-// Package matching ports name/member matching from scripts/match_payments.py.
+// Package matching ports name/member matching from legacy/scripts/match_payments.py.
 package matching

go/internal/domain/matching/format_date.go

@@ -14,7 +14,7 @@ var sheetsEpoch = time.Date(1899, 12, 30, 0, 0, 0, 0, time.UTC)
 // a pre-formatted "YYYY-MM-DD" string (returned as-is), or any other value
 // (returned as fmt.Sprint(v).TrimSpace). Never returns an error.
 //
-// Ports scripts/match_payments.py format_date.
+// Ports legacy/scripts/match_payments.py format_date.
 func FormatDate(val any) string {
 	if val == nil {
 		return ""

go/internal/domain/matching/format_date_test.go

@@ -1,8 +1,8 @@
 package matching
 
-// Expected values verified against scripts/match_payments.py on 2026-05-06:
+// Expected values verified against legacy/scripts/match_payments.py on 2026-05-06:
 //
-//	PYTHONPATH=scripts:. python3 -c '
+//	PYTHONPATH=legacy/scripts:legacy python3 -c '
 //	from match_payments import format_date
 //	for v in [None, "", 44197, 44197.5, "2026-04-15", "garbage", "  2026-04-15  "]:
 //	    print(repr(format_date(v)))

go/internal/domain/matching/infer.go

@@ -33,7 +33,7 @@ type InferredDetails struct {
 // defaultYear seeds czech.ParseMonthReferences (Python defaulted to the current year;
 // callers should pass time.Now().Year() or a fixed year for deterministic tests).
 //
-// Ports scripts/match_payments.py infer_transaction_details.
+// Ports legacy/scripts/match_payments.py infer_transaction_details.
 func InferTransactionDetails(tx Transaction, memberNames []string, defaultYear int) InferredDetails {
 	searchText := fmt.Sprintf("%s %s %s", tx.Sender, tx.Message, tx.UserID)
 

go/internal/domain/matching/infer_test.go

@@ -1,8 +1,8 @@
 package matching
 
-// Expected values verified against scripts/match_payments.py on 2026-05-06:
+// Expected values verified against legacy/scripts/match_payments.py on 2026-05-06:
 //
-//	PYTHONPATH=scripts:. python3 << 'EOF'
+//	PYTHONPATH=legacy/scripts:legacy python3 << 'EOF'
 //	from match_payments import infer_transaction_details
 //	MEMBERS = ["Tomáš Němeček (Tov)", "Jana Nováková"]
 //	cases = [

go/internal/domain/matching/match_members.go

@@ -28,7 +28,7 @@ var commonSurnames = map[string]bool{
 // MatchMembers finds members mentioned in text and returns them with a
 // confidence level of "auto" (reliable) or "review" (needs human verification).
 //
-// Algorithm (ported verbatim from scripts/match_payments.py match_members):
+// Algorithm (ported verbatim from legacy/scripts/match_payments.py match_members):
 //  1. Exact short-circuit: if any member's full normalized name appears as whole
 //     words in normalize(text), return ONLY those matches as auto. This prevents
 //     nickname "tov" from matching inside surname "ottova".

go/internal/domain/matching/match_members_test.go

@@ -1,9 +1,9 @@
 package matching
 
-// Expected values verified against scripts/match_payments.py and
+// Expected values verified against legacy/scripts/match_payments.py and
 // tests/test_match_members.py on 2026-05-06:
 //
-//	PYTHONPATH=scripts:. python3 -c '
+//	PYTHONPATH=legacy/scripts:legacy python3 -c '
 //	from match_payments import match_members
 //	MEMBERS = ["Henrietta Ottová", "Tomáš Němeček (Tov)", "František Vrbík (Štrúdl)", "Jana Nováková"]
 //	cases = [

go/internal/domain/matching/name_variants.go

@@ -19,7 +19,7 @@ var (
 // this invariant for the exact short-circuit pass. Variants shorter than 3 characters are
 // dropped.
 //
-// Ports scripts/match_payments.py _build_name_variants.
+// Ports legacy/scripts/match_payments.py _build_name_variants.
 func BuildNameVariants(name string) []string {
 	var nickname string
 	if m := nicknameRe.FindStringSubmatch(name); m != nil {

go/internal/domain/matching/name_variants_test.go

@@ -1,8 +1,8 @@
 package matching
 
-// Expected values verified against scripts/match_payments.py on 2026-05-06:
+// Expected values verified against legacy/scripts/match_payments.py on 2026-05-06:
 //
-//	PYTHONPATH=scripts:. python3 -c '
+//	PYTHONPATH=legacy/scripts:legacy python3 -c '
 //	from match_payments import _build_name_variants
 //	for n in ["František Vrbík (Štrúdl)", "Tov (St)", "Jana", "  Petr  Novák  ( Jenda ) "]:
 //	    print(repr(n), "->", _build_name_variants(n))