feat(go): add --print-fio-table flag to fuj sync --dry-run

Prints an aligned tabwriter table of every Fio transaction in the
look-back window, with a STATUS column showing NEW (would be appended)
or DUP (already in sheet). Only fires when --dry-run is also set, so
it can't affect real syncs. Refactors Sync ID computation into a single
pre-pass shared by both the table printer and the row builder.

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

go/internal/services/banksync/sync.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"fuj-management/go/internal/domain/synch"
 	"fuj-management/go/internal/io/fio"
+	"os"
 	"strings"
 	"time"
 )
@@ -27,10 +28,11 @@ type sheetsWriter interface {
 
 // SyncOpts controls the date window and sort behaviour.
 type SyncOpts struct {
-	Days     int       // look-back window when From/To are zero
-	From, To time.Time // explicit window (overrides Days)
-	Sort     bool      // sort the sheet by Date after appending
-	DryRun   bool      // print planned writes without modifying the sheet
+	Days          int       // look-back window when From/To are zero
+	From, To      time.Time // explicit window (overrides Days)
+	Sort          bool      // sort the sheet by Date after appending
+	DryRun        bool      // print planned writes without modifying the sheet
+	PrintFioTable bool      // with DryRun: print every fetched Fio txn with NEW/DUP status
 }
 
 // SyncToSheets fetches Fio transactions and appends new ones to the payments sheet.
@@ -92,14 +94,14 @@ func SyncToSheets(
 			from.Format("2006-01-02"), to.Format("2006-01-02"), len(txns))
 	}
 
-	// 4. Append new rows.
-	var newRows [][]any
-	for _, tx := range txns {
+	// 4a. Compute Sync IDs for every fetched txn (shared by table-print and row-build).
+	syncIDs := make([]string, len(txns))
+	for i, tx := range txns {
 		currency := tx.Currency
 		if currency == "" {
 			currency = "CZK"
 		}
-		id := synch.GenerateSyncID(synch.Transaction{
+		syncIDs[i] = synch.GenerateSyncID(synch.Transaction{
 			Date:     tx.Date,
 			Amount:   tx.Amount,
 			Currency: currency,
@@ -108,13 +110,23 @@ func SyncToSheets(
 			Message:  tx.Message,
 			BankID:   tx.BankID,
 		})
-		if existingIDs[id] {
+	}
+
+	// 4b. Optional debug table (dry-run only).
+	if opts.DryRun && opts.PrintFioTable {
+		printFioTable(os.Stdout, txns, syncIDs, existingIDs)
+	}
+
+	// 4c. Build new rows.
+	var newRows [][]any
+	for i, tx := range txns {
+		if existingIDs[syncIDs[i]] {
 			continue
 		}
 		newRows = append(newRows, []any{
 			tx.Date, tx.Amount,
 			"", "", "", "", // manual fix, Person, Purpose, Inferred Amount
-			tx.Sender, tx.VS, tx.Message, tx.BankID, id,
+			tx.Sender, tx.VS, tx.Message, tx.BankID, syncIDs[i],
 		})
 	}