feat(go/M2.11-12): wire fuj fees + fuj reconcile subcommands

Add internal/services/membership package: AttendanceLoader,
TransactionLoader, ExceptionLoader interfaces + NewStubSources stub
(returns ErrIOPending until M4 lands real Sheets loaders).

FeesReport and ReconcileReport orchestrate domain/fees + domain/reconcile
and write fixed-width text reports matching Python calculate_fees.py and
match_payments.py print_report output. 13 unit tests cover all formatter
branches and orchestration wiring via fake loaders.

cmd/fuj/main.go: fees and reconcile subcommands now dispatch; sync/infer
retain the [M4] placeholder.

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

CHANGELOG.md

@@ -1,5 +1,13 @@
 # Changelog
 
+## 2026-05-06 17:49 CEST — feat(go/M2.11-12): wire fuj fees + fuj reconcile subcommands
+
+- New `go/internal/services/membership` package: `AttendanceLoader`, `TransactionLoader`, `ExceptionLoader` interfaces, a stub (`NewStubSources`) that returns `ErrIOPending`, and `FeesReport` / `ReconcileReport` orchestration functions backed by real `domain/fees` + `domain/reconcile` logic.
+- Text formatters `printFeesTable` / `printReconcileReport` port the output of `calculate_fees.py` and `match_payments.py print_report` verbatim.
+- `cmd/fuj/main.go`: `fuj fees` and `fuj reconcile` subcommands now dispatch properly; `fuj sync` / `fuj infer` retain the [M4] placeholder.
+- Both subcommands exit 1 with a clean `"io layer not yet wired up; lands in milestone M4"` message until real Sheets loaders are injected in M4.
+- 13 unit tests covering stubs, all formatter branches (OK/partial/UNPAID/dash cells, credits, debts, unmatched, review annotation), and orchestration wiring via fake loaders.
+
 ## 2026-05-06 16:38 CEST — fix: include juniors in payment-inference roster
 
 - `scripts/infer_payments.py`: union adults + junior rosters so junior-only members are visible to the matcher.