sign_tx: move btc fee confirmation impl to sign_utils

diff --git a/main/process/sign_tx.c b/main/process/sign_tx.c
index f097cf6..cb40b09 100644
--- a/main/process/sign_tx.c
+++ b/main/process/sign_tx.c
@@ -333,50 +333,6 @@ cleanup:
     return true;
 }
 
-bool show_btc_fee_confirmation_activity(const network_t network_id, const struct wally_tx* tx,
-    const output_info_t* outinfo, const script_flavour_t aggregate_inputs_scripts_flavour, const uint64_t input_amount,
-    const uint64_t output_amount)
-{
-    JADE_ASSERT(tx);
-    // outputinfo is optional
-    JADE_ASSERT(input_amount);
-    JADE_ASSERT(output_amount);
-
-    JADE_ASSERT(input_amount >= output_amount);
-
-    // User to agree fee amount
-    // The fee amount is the shortfall between input and output amounts
-    // The 'spend' amount is the total of the outputs not flagged as change
-    const uint64_t fees = input_amount - output_amount;
-    uint64_t spend_amount = output_amount;
-    if (outinfo) {
-        for (size_t i = 0; i < tx->num_outputs; ++i) {
-            if (outinfo[i].flags & OUTPUT_FLAG_CHANGE) {
-                // Deduct change output amount
-                JADE_ASSERT(spend_amount >= tx->outputs[i].satoshi);
-                spend_amount -= tx->outputs[i].satoshi;
-            }
-        }
-    }
-
-    char warnbuf[128]; // sufficient
-    const char* warning_msg = NULL;
-    const bool warn_fees = fees && fees >= spend_amount;
-    const bool warn_scripts = aggregate_inputs_scripts_flavour == SCRIPT_FLAVOUR_MIXED;
-    if (warn_fees && warn_scripts) {
-        const int retval = snprintf(warnbuf, sizeof(warnbuf), "%s %s", WARN_MSG_HIGH_FEES, WARN_MSG_MIXED_INPUTS);
-        JADE_ASSERT(retval > 0 && retval < sizeof(warnbuf));
-        warning_msg = warnbuf;
-    } else if (warn_scripts) {
-        warning_msg = WARN_MSG_MIXED_INPUTS;
-    } else if (warn_fees) {
-        warning_msg = WARN_MSG_HIGH_FEES;
-    }
-
-    // Return whether the user accepts or declines
-    return show_btc_final_confirmation_activity(network_id, fees, warning_msg);
-}
-
 // Loop to generate and send Anti-Exfil signatures as they are requested.
 static void send_ae_signature_replies(const network_t network_id, jade_process_t* process, signing_data_t* signing_data)
 {
diff --git a/main/process/sign_utils.c b/main/process/sign_utils.c
index 86de814..763548a 100644
--- a/main/process/sign_utils.c
+++ b/main/process/sign_utils.c
@@ -631,6 +631,49 @@ done:
     return true;
 }
 
+bool show_btc_fee_confirmation_activity(const network_t network_id, const struct wally_tx* tx, const output_info_t* outinfo,
+    const script_flavour_t aggregate_inputs_scripts_flavour, const uint64_t input_amount, const uint64_t output_amount)
+{
+    JADE_ASSERT(tx);
+    // outputinfo is optional
+    JADE_ASSERT(input_amount);
+    JADE_ASSERT(output_amount);
+
+    JADE_ASSERT(input_amount >= output_amount);
+
+    // User to agree fee amount
+    // The fee amount is the shortfall between input and output amounts
+    // The 'spend' amount is the total of the outputs not flagged as change
+    const uint64_t fees = input_amount - output_amount;
+    uint64_t spend_amount = output_amount;
+    if (outinfo) {
+        for (size_t i = 0; i < tx->num_outputs; ++i) {
+            if (outinfo[i].flags & OUTPUT_FLAG_CHANGE) {
+                // Deduct change output amount
+                JADE_ASSERT(spend_amount >= tx->outputs[i].satoshi);
+                spend_amount -= tx->outputs[i].satoshi;
+            }
+        }
+    }
+
+    char warnbuf[128]; // sufficient
+    const char* warning_msg = NULL;
+    const bool warn_fees = fees && fees >= spend_amount;
+    const bool warn_scripts = aggregate_inputs_scripts_flavour == SCRIPT_FLAVOUR_MIXED;
+    if (warn_fees && warn_scripts) {
+        const int retval = snprintf(warnbuf, sizeof(warnbuf), "%s %s", WARN_MSG_HIGH_FEES, WARN_MSG_MIXED_INPUTS);
+        JADE_ASSERT(retval > 0 && retval < sizeof(warnbuf));
+        warning_msg = warnbuf;
+    } else if (warn_scripts) {
+        warning_msg = WARN_MSG_MIXED_INPUTS;
+    } else if (warn_fees) {
+        warning_msg = WARN_MSG_HIGH_FEES;
+    }
+
+    // Return whether the user accepts or declines
+    return show_btc_final_confirmation_activity(network_id, fees, warning_msg);
+}
+
 bool show_elements_fee_confirmation_activity(const network_t network_id, const struct wally_tx* tx,
     const output_info_t* outinfo, const script_flavour_t aggregate_inputs_scripts_flavour, const uint64_t fees,
     const TxType_t txtype, const bool is_partial)