Refactor: Use Dialog for PhotoViewScreen

This commit refactors the PhotoViewScreen to be displayed as a Dialog instead of a separate navigation destination.

Key changes:
- Introduced `PhotoViewDialog` composable that wraps `PhotoViewRoute` in a `FullScreenDialog`.
- Modified `RootScreen` to use `PhotoViewDialog` for displaying images.
- Updated `PhotoViewViewModelImpl` to handle loading state and display a loader while downloading images.
- Made `Loader` and `ContainedLoader` colors configurable.
- Adjusted `PhotoViewScreen` UI:
    - Set background to translucent black.
    - Updated TopAppBar background color and icon tints.
    - Improved vertical drag gesture for dismissing the viewer.
- Made `VkUserData.LastSeen.platform` nullable.
- Removed unused navigation functions related to the old PhotoViewScreen.

core/ui/src/main/kotlin/dev/meloda/fast/ui/components/FullScreenDialog.kt

@@ -0,0 +1,33 @@
+package dev.meloda.fast.ui.components
+
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.window.Dialog
+import androidx.compose.ui.window.DialogProperties
+import androidx.compose.ui.zIndex
+
+@Composable
+fun FullScreenDialog(
+    modifier: Modifier = Modifier,
+    content: @Composable () -> Unit
+) {
+    Dialog(
+        onDismissRequest = {},
+        DialogProperties(
+            usePlatformDefaultWidth = false,
+            decorFitsSystemWindows = false
+        )
+    ) {
+        Box(
+            modifier = modifier
+                .fillMaxSize()
+                .zIndex(10F),
+            contentAlignment = Alignment.Center
+        ) {
+            content()
+        }
+    }
+}

core/ui/src/main/kotlin/dev/meloda/fast/ui/components/Loaders.kt

@@ -10,52 +10,70 @@ import androidx.compose.material3.MaterialTheme
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.tooling.preview.Preview
 
 @Composable
 @Preview
-fun FullScreenContainedLoader(modifier: Modifier = Modifier) {
+fun FullScreenContainedLoader(
+    modifier: Modifier = Modifier,
+    containerColor: Color = MaterialTheme.colorScheme.primary,
+    indicatorColor: Color = MaterialTheme.colorScheme.primaryContainer
+) {
     Box(
         modifier = modifier
             .fillMaxSize()
             .navigationBarsPadding(),
         contentAlignment = Alignment.Center
     ) {
-        ContainedLoader()
+        ContainedLoader(
+            containerColor = containerColor,
+            indicatorColor = indicatorColor
+        )
     }
 }
 
 @Preview
 @Composable
-fun FullScreenLoader(modifier: Modifier = Modifier) {
+fun FullScreenLoader(
+    modifier: Modifier = Modifier,
+    color: Color = MaterialTheme.colorScheme.primary
+) {
     Box(
         modifier = modifier
             .fillMaxSize()
             .navigationBarsPadding(),
         contentAlignment = Alignment.Center
     ) {
-        Loader()
+        Loader(color = color)
     }
 }
 
 @OptIn(ExperimentalMaterial3ExpressiveApi::class)
 @Composable
 @Preview
-fun ContainedLoader(modifier: Modifier = Modifier) {
+fun ContainedLoader(
+    modifier: Modifier = Modifier,
+    containerColor: Color = MaterialTheme.colorScheme.primary,
+    indicatorColor: Color = MaterialTheme.colorScheme.primaryContainer
+) {
     ContainedLoadingIndicator(
         modifier = modifier,
-        containerColor = MaterialTheme.colorScheme.primary,
-        indicatorColor = MaterialTheme.colorScheme.primaryContainer
+        containerColor = containerColor,
+        indicatorColor = indicatorColor
     )
 }
 
 @OptIn(ExperimentalMaterial3ExpressiveApi::class)
 @Composable
 @Preview
-fun Loader(modifier: Modifier = Modifier) {
+fun Loader(
+    modifier: Modifier = Modifier,
+    color: Color = MaterialTheme.colorScheme.primary
+) {
     LoadingIndicator(
         modifier = modifier,
-        color = MaterialTheme.colorScheme.primary
+        color = color
     )
 }