chore: tick M2.3 + M2.4 in progress tracker + CHANGELOG entry

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

CHANGELOG.md

@@ -1,5 +1,12 @@
 # Changelog
 
+## 2026-05-06 09:24 CEST — feat(go/M2.3+M2.4): port domain/fees.CalculateFee and CalculateJuniorFee
+
+- New `go/internal/domain/fees` package with adult and junior fee calculators ported from `scripts/attendance.py`.
+- `CalculateFee(count, monthKey) int` — `0→0`, `1→200`, `2+→AdultFeeMonthlyRate[month]` (fallback 700 CZK).
+- `CalculateJuniorFee(count, monthKey) Expected` — `0→{0}`, `1→{Unknown:true}` (the `"?"` sentinel, now strictly typed), `2+→JuniorFeeMonthlyRate[month]` (fallback 500 CZK).
+- 20 table-driven tests, all verified against live Python; `-race` clean; `golangci-lint` clean.
+
 ## 2026-05-06 00:07 CEST — feat(go/M2.2): port czech.ParseMonthReferences
 
 - `internal/domain/czech.ParseMonthReferences`: three-pass regex (numeric slash, dot, Czech month names) with range wrap-around and `m≥10 → previousYear` heuristic, byte-equivalent to Python.

docs/plans/2026-05-03-2349-go-backend-rewrite-progress.md

@@ -4,7 +4,7 @@ Companion to [2026-05-03-2349-go-backend-rewrite.md](2026-05-03-2349-go-backend-
 
 **Current milestone:** M2 — Pure-domain helpers
 **Started:** 2026-05-04
-**Last updated:** 2026-05-04
+**Last updated:** 2026-05-06
 
 ## How to use
 
@@ -46,8 +46,8 @@ Each task: port the function, write Go unit tests for fresh cases, hook into the
 
 - [x] **M2.1** `domain/czech.Normalize` — port [czech_utils.py](scripts/czech_utils.py) `normalize` (NFKD + combining-mark strip + lowercase) — `20ade6d`
 - [x] **M2.2** `domain/czech.ParseMonthReferences` — port `parse_month_references` (45 month declensions, range wrap, year inference) — `0a8017f`
-- [ ] **M2.3** `domain/fees.CalculateFee` — port [attendance.py](scripts/attendance.py) `calculate_fee` (constants table)
-- [ ] **M2.4** `domain/fees.CalculateJuniorFee` — port `calculate_junior_fee` with `Expected{Value int; Unknown bool}` for the `"?"` sentinel
+- [x] **M2.3** `domain/fees.CalculateFee` — port [attendance.py](scripts/attendance.py) `calculate_fee` (constants table) — `0fc3b6d`
+- [x] **M2.4** `domain/fees.CalculateJuniorFee` — port `calculate_junior_fee` with `Expected{Value int; Unknown bool}` for the `"?"` sentinel — `0fc3b6d`
 - [ ] **M2.5** `domain/money.ParseCZK` — port [infer_payments.py](scripts/infer_payments.py) `parse_czk_amount` (Czech locale: comma decimal, dot/space thousand separators)
 - [ ] **M2.6** `domain/synch.GenerateSyncID` — port [sync_fio_to_sheets.py](scripts/sync_fio_to_sheets.py) `generate_sync_id` (SHA-256, byte-stable hash; verify float string format against real sheet rows)
 - [ ] **M2.7** `domain/matching.BuildNameVariants` + `MatchMembers` — port `_build_name_variants` and `match_members` from [match_payments.py](scripts/match_payments.py) (auto vs review confidence, common-surname filter)