fix(core): show label prefix during BLE pairing

diff --git a/core/embed/rust/src/trezorhal/ble/micropython.rs b/core/embed/rust/src/trezorhal/ble/micropython.rs
index 5349d6c3..4d4933f5 100644
--- a/core/embed/rust/src/trezorhal/ble/micropython.rs
+++ b/core/embed/rust/src/trezorhal/ble/micropython.rs
@@ -65,12 +65,12 @@ extern "C" fn py_start_advertising(whitelist: Obj, name: Obj) -> Obj {
         let name = name.try_into_option::<StrBuffer>()?;
         let name = name.as_deref().unwrap_or(model::FULL_NAME);
 
-        if whitelist {
-            switch_on(name)?;
+        let adv_name = if whitelist {
+            switch_on(name)?
         } else {
-            pairing_mode(name)?;
+            pairing_mode(name)?
         };
-        Ok(Obj::const_none())
+        adv_name.try_into()
     };
     unsafe { util::try_or_raise(block) }
 }
@@ -339,7 +339,7 @@ pub static mp_module_trezorble: Module = obj_module! {
     ///     """
     Qstr::MP_QSTR_start_comm => obj_fn_0!(py_start_comm).as_obj(),
 
-    /// def start_advertising(whitelist: bool, name: str | None):
+    /// def start_advertising(whitelist: bool, name: str | None) -> str:
     ///     """
     ///     Start advertising.
     ///     Raises exception if BLE driver reports an error.
diff --git a/core/embed/rust/src/trezorhal/ble/mod.rs b/core/embed/rust/src/trezorhal/ble/mod.rs
index dc250d06..aa6a250a 100644
--- a/core/embed/rust/src/trezorhal/ble/mod.rs
+++ b/core/embed/rust/src/trezorhal/ble/mod.rs
@@ -18,12 +18,12 @@ const COMMAND_FAILED: Error = Error::RuntimeError(c"BLE command failed");
 const WRITE_FAILED: Error = Error::RuntimeError(c"BLE write failed");
 
 // NOTE: replace with floor_char_boundary when stable
-fn prefix_utf8_bytes(text: &str, max_len: usize) -> &[u8] {
+fn prefix_utf8_bytes(text: &str, max_len: usize) -> &str {
     let mut i = text.len().min(max_len);
     while !text.is_char_boundary(i) {
         i -= 1;
     }
-    &text.as_bytes()[..i]
+    &text[..i]
 }
 
 pub fn res_to_result(res: bool) -> Result<(), Error> {
@@ -83,16 +83,18 @@ fn state() -> ffi::ble_state_t {
     state
 }
 
-pub fn pairing_mode(name: &str) -> Result<(), Error> {
-    let name = prefix_utf8_bytes(name, ADV_NAME_LEN);
-    let res = unsafe { ffi::ble_enter_pairing_mode(name.as_ptr(), name.len()) };
-    res_to_result(res)
+pub fn pairing_mode(name: &str) -> Result<&str, Error> {
+    let adv_name = prefix_utf8_bytes(name, ADV_NAME_LEN);
+    let res = unsafe { ffi::ble_enter_pairing_mode(adv_name.as_ptr(), adv_name.len()) };
+    res_to_result(res)?;
+    Ok(adv_name)
 }
 
-pub fn switch_on(name: &str) -> Result<(), Error> {
-    set_name(name);
+pub fn switch_on(name: &str) -> Result<&str, Error> {
+    let adv_name = set_name(name);
     let res = unsafe { ffi::ble_switch_on() };
-    res_to_result(res)
+    res_to_result(res)?;
+    Ok(adv_name)
 }
 
 pub fn switch_off() -> Result<(), Error> {
@@ -148,9 +150,10 @@ pub fn disconnect() -> Result<(), Error> {
     res_to_result(res)
 }
 
-pub fn set_name(name: &str) {
-    let bytes = prefix_utf8_bytes(name, ADV_NAME_LEN);
-    unsafe { ffi::ble_set_name(bytes.as_ptr(), bytes.len()) }
+pub fn set_name(name: &str) -> &str {
+    let adv_name = prefix_utf8_bytes(name, ADV_NAME_LEN);
+    unsafe { ffi::ble_set_name(adv_name.as_ptr(), adv_name.len()) }
+    adv_name
 }
 
 pub fn set_high_speed(enable: bool) {
diff --git a/core/mocks/generated/trezorble.pyi b/core/mocks/generated/trezorble.pyi
index c91dab08..19e26a04 100644
--- a/core/mocks/generated/trezorble.pyi
+++ b/core/mocks/generated/trezorble.pyi
@@ -55,7 +55,7 @@ def start_comm():
 
 
 # rust/src/trezorhal/ble/micropython.rs
-def start_advertising(whitelist: bool, name: str | None):
+def start_advertising(whitelist: bool, name: str | None) -> str:
     """
     Start advertising.
     Raises exception if BLE driver reports an error.
diff --git a/core/src/apps/management/ble/pair_new_device.py b/core/src/apps/management/ble/pair_new_device.py
index d4f3da1a..995599ac 100644
--- a/core/src/apps/management/ble/pair_new_device.py
+++ b/core/src/apps/management/ble/pair_new_device.py
@@ -36,7 +36,7 @@ async def pair_new_device() -> None:
     from trezor import TR
 
     label = storage_device.get_label() or _default_ble_name()
-    ble.start_advertising(False, label)
+    label = ble.start_advertising(False, label)
     result = None
     try:
         code = await interact(
@@ -65,4 +65,4 @@ async def pair_new_device() -> None:
     finally:
         if result is not CONFIRMED:
             ble.reject_pairing()
-        ble.set_name(storage_device.get_label())
+        ble.set_name(label)