chore: Remove ui from main activity, moving it calendar act

This removes the layout & any graphical elements that were used in the
main activity, making it purely a transitional activity (either leading
to the login activity, or to the calendar activity).

.idea/gradle.xml

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
+  <component name="GradleMigrationSettings" migrationVersion="1" />
   <component name="GradleSettings">
     <option name="linkedExternalProjectsSettings">
       <GradleProjectSettings>

.idea/misc.xml

@@ -1,4 +1,3 @@
-<?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="ExternalStorageConfigurationManager" enabled="true" />
   <component name="ProjectRootManager" version="2" languageLevel="JDK_21" default="true" project-jdk-name="jbr-21" project-jdk-type="JavaSDK">

app/src/main/AndroidManifest.xml

@@ -16,6 +16,9 @@
         android:supportsRtl="true"
         android:theme="@style/Theme.NeatCalendar"
         tools:targetApi="31">
+        <activity
+            android:name=".CalendarActivity"
+            android:exported="false" />
         <activity
             android:name=".ApiUnreachableActivity"
             android:exported="false" />

app/src/main/java/com/p_vacho/neat_calendar/CalendarActivity.kt

@@ -0,0 +1,26 @@
+package com.p_vacho.neat_calendar
+
+import android.os.Bundle
+import androidx.activity.enableEdgeToEdge
+import androidx.appcompat.app.AppCompatActivity
+import androidx.core.view.ViewCompat
+import androidx.core.view.WindowInsetsCompat
+
+class CalendarActivity : AppCompatActivity() {
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        enableEdgeToEdge()
+        setContentView(R.layout.activity_calendar)
+        ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main)) { v, insets ->
+            val systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars())
+            v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom)
+            insets
+        }
+
+        initializeCalendar()
+    }
+
+    private fun initializeCalendar() {
+        // TODO("Not yet implemented")
+    }
+}

app/src/main/java/com/p_vacho/neat_calendar/MainActivity.kt

@@ -2,11 +2,8 @@ package com.p_vacho.neat_calendar
 
 import android.content.Intent
 import android.os.Bundle
-import androidx.activity.enableEdgeToEdge
 import androidx.appcompat.app.AppCompatActivity
 import androidx.core.splashscreen.SplashScreen.Companion.installSplashScreen
-import androidx.core.view.ViewCompat
-import androidx.core.view.WindowInsetsCompat
 import com.p_vacho.neat_calendar.api.RetrofitClient
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
@@ -24,20 +21,11 @@ class MainActivity : AppCompatActivity() {
         splashScreen.setKeepOnScreenCondition { !loggedIn }
 
         super.onCreate(savedInstanceState)
-        enableEdgeToEdge()
-        setContentView(R.layout.activity_main)
 
         // Perform initialization (login check)
         CoroutineScope(Dispatchers.Main).launch {
             initialize()
         }
-
-        // Handle window insets for proper layout adjustment
-        ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main)) { v, insets ->
-            val systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars())
-            v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom)
-            insets
-        }
     }
 
     private suspend fun initialize() {
@@ -53,6 +41,8 @@ class MainActivity : AppCompatActivity() {
         if (!loggedIn) {
             navigateToLoginActivity()
         }
+
+        navigateToCalendarActivity()
     }
 
     private suspend fun checkUserLogin(): Boolean {
@@ -73,4 +63,11 @@ class MainActivity : AppCompatActivity() {
         startActivity(intent)
         finish() // Close MainActivity
     }
+
+    private fun navigateToCalendarActivity() {
+        val intent = Intent(this, CalendarActivity::class.java)
+        intent.flags = Intent.FLAG_ACTIVITY_CLEAR_TOP or Intent.FLAG_ACTIVITY_NEW_TASK
+        startActivity(intent)
+        finish() // Close MainActivity
+    }
 }

app/src/main/res/layout/activity_calendar.xml

@@ -5,7 +5,7 @@
     android:id="@+id/main"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
-    tools:context=".MainActivity">
+    tools:context=".CalendarActivity">
 
     <TextView
         android:layout_width="wrap_content"