🧪 Test PairingCodeEntryViewModel onManualCodeChange (#512)

* Test PairingCodeEntryViewModel onManualCodeChange

Added unit tests to cover the `onManualCodeChange` function in `PairingCodeEntryViewModel`.
The test validates that the function properly updates the state and handles string trimming
as well as error message clearance.

Changes include:
- Created `PairingCodeEntryViewModelTest.kt` in `app/src/test/java/com/m57/hermescontrol/ui/pairing/`
- Implemented `testOnManualCodeChange_updatesStateAndClearsError` to check correct state update logic and verify error clear functionality.
- Implemented `testOnManualCodeChange_trimsInput` to verify input is properly trimmed.
- Added necessary mock setup to deal with Android components (`Application` and `android.util.Log`).

* Fix ktlint format issue in PairingCodeEntryViewModelTest

Ran `ktlint --format` to fix the `standard:no-empty-first-line-in-class-body`
formatting violation introduced in the previous commit.

app/src/test/java/com/m57/hermescontrol/ui/pairing/PairingCodeEntryViewModelTest.kt

@@ -0,0 +1,55 @@
+package com.m57.hermescontrol.ui.pairing
+
+import android.app.Application
+import android.util.Log
+import io.mockk.every
+import io.mockk.mockk
+import io.mockk.mockkStatic
+import io.mockk.unmockkAll
+import org.junit.After
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
+import org.junit.Before
+import org.junit.Test
+
+class PairingCodeEntryViewModelTest {
+    private val mockApp: Application = mockk(relaxed = true)
+
+    @Before
+    fun setup() {
+        mockkStatic(Log::class)
+        every { Log.d(any(), any()) } returns 0
+        every { Log.e(any(), any(), any()) } returns 0
+    }
+
+    @After
+    fun teardown() {
+        unmockkAll()
+    }
+
+    @Test
+    fun testOnManualCodeChange_updatesStateAndClearsError() {
+        val viewModel = PairingCodeEntryViewModel(mockApp)
+
+        // Force an error to verify it gets cleared
+        // using onCodeDetected with invalid input to set the error
+        viewModel.onCodeDetected("invalid-code")
+        assertEquals(true, viewModel.uiState.value.errorMessage != null)
+
+        viewModel.onManualCodeChange("new-code")
+
+        val state = viewModel.uiState.value
+        assertEquals("new-code", state.manualCode)
+        assertNull(state.errorMessage)
+    }
+
+    @Test
+    fun testOnManualCodeChange_trimsInput() {
+        val viewModel = PairingCodeEntryViewModel(mockApp)
+
+        viewModel.onManualCodeChange("  trimmed-code  \n")
+
+        val state = viewModel.uiState.value
+        assertEquals("trimmed-code", state.manualCode)
+    }
+}