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>

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

@@ -54,8 +54,8 @@ Each task: port the function, write Go unit tests for fresh cases, hook into the
 - [x] **M2.8** `domain/matching.InferTransactionDetails` — port `infer_transaction_details` (composes name + month parsing) — `e596f00`
 - [x] **M2.9** `domain/matching.FormatDate` — port `format_date` (handles Google Sheets serial-day numbers since 1899-12-30) — `e596f00`
 - [x] **M2.10** `domain/reconcile.Reconcile` — port `reconcile` (three-phase allocation: greedy / proportional with float-remainder absorption / even-split fallback). The single most load-bearing function; budget extra time. — `c53bf5a`
-- [ ] **M2.11** `fuj fees` subcommand wired up via `domain/fees` + (M4-stub) attendance loader — fail gracefully on missing IO until M4 lands
-- [ ] **M2.12** `fuj reconcile` subcommand similarly stubbed
+- [x] **M2.11** `fuj fees` subcommand wired up via `domain/fees` + (M4-stub) attendance loader — fail gracefully on missing IO until M4 lands
+- [x] **M2.12** `fuj reconcile` subcommand similarly stubbed
 
 **Gate:** `cd go && go test -tags=parity ./tests/parity/pure/...` green for every fixture in `tests/fixtures/pure/`.