Add dependency wiring, token storage, and app entry points

- AppDependencies: manual DI container with lazy singletons
- TokenStore: DataStore-backed persistence for server URL, access token,
  theme preference, and accent color selection
- DataStoreFactory: multiplatform DataStore creation
- LocalAppDependencies: CompositionLocal for DI access in composables
- App.kt: root composable with theme + Coil ImageLoader (Ktor engine)
- MainActivity: creates AppDependencies, provides via CompositionLocal
- Coil configured with authenticated Ktor HttpClient for private images

Co-Authored-By: Claude Opus 4.6 (1M context)

Signed-off-by: Avinal Kumar <avinal.xlvii@gmail.com>

androidApp/src/main/kotlin/com/avinal/memos/MainActivity.kt

@@ -0,0 +1,29 @@
+package com.avinal.memos
+
+import android.os.Bundle
+import androidx.activity.ComponentActivity
+import androidx.activity.compose.setContent
+import androidx.activity.enableEdgeToEdge
+import androidx.compose.runtime.CompositionLocalProvider
+import com.avinal.memos.util.LocalAppDependencies
+
+class MainActivity : ComponentActivity() {
+
+    private val deps by lazy {
+        AppDependencies(
+            dataStorePath = filesDir.resolve("memos_prefs.preferences_pb").absolutePath,
+            platformContext = applicationContext,
+        )
+    }
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        deps.initialize()
+        enableEdgeToEdge()
+        setContent {
+            CompositionLocalProvider(LocalAppDependencies provides deps) {
+                App()
+            }
+        }
+    }
+}