fix: restore test-used functions, silence tx.Rollback closed errors, prune knip dead code

Restore processImage (images.go) and nonDepositPaymentType (handlers.go) with //nolint:unused — used in test files.
Fix 97 tx.Rollback defers to silently discard expected "tx is closed" error after commit.
Frontend: remove 44 unused shadcn-svelte files, 2 dead components, 9 stale npm deps, prune unused exports.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/auth/jwt.go

@@ -49,7 +49,7 @@ func RevokeJTI(ctx context.Context, jti string, expiresAt time.Time) {
 		return
 	}
 	defer func() {
-    if err := tx.Rollback(ctx); err != nil {
+    if err := tx.Rollback(ctx); err != nil && err.Error() != "tx is closed" {
         slog.Error("failed to rollback transaction", "err", err)
     }
 }()
@@ -98,7 +98,7 @@ func CleanupRevokedJTIs(ctx context.Context) (int, error) {
 		return 0, err
 	}
 	defer func() {
-    if err := tx.Rollback(ctx); err != nil {
+    if err := tx.Rollback(ctx); err != nil && err.Error() != "tx is closed" {
         slog.Error("failed to rollback transaction", "err", err)
     }
 }()
@@ -208,7 +208,7 @@ func GenerateRefreshToken(ctx context.Context, userID string, role string) (stri
 		return "", fmt.Errorf("failed to begin transaction: %w", err)
 	}
 	defer func() {
-    if err := tx.Rollback(ctx); err != nil {
+    if err := tx.Rollback(ctx); err != nil && err.Error() != "tx is closed" {
         slog.Error("failed to rollback transaction", "err", err)
     }
 }()
@@ -241,7 +241,7 @@ func VerifyRefreshToken(ctx context.Context, tokenString string) (userID string,
 		return "", "", fmt.Errorf("failed to begin transaction: %w", err)
 	}
 	defer func() {
-    if err := tx.Rollback(ctx); err != nil {
+    if err := tx.Rollback(ctx); err != nil && err.Error() != "tx is closed" {
         slog.Error("failed to rollback transaction", "err", err)
     }
 }()