feat: Add Android Adaptive Icons support

Implement adaptive icons for Android 8.0 (API 26) and above following official Android guidelines.

Changes:
- Create mipmap-anydpi-v26 directory with ic_launcher.xml and ic_launcher_round.xml
- Add ic_launcher_foreground.xml with V2EX logo scaled for 108dp canvas
- Add ic_launcher_background.xml with solid color background
- Support monochrome layer for Android 13+ Material You theming
- Maintain backward compatibility with existing PNG icons for older devices

The implementation uses the existing logo_svg.xml and respects day/night theme colors.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: graycreate

app/src/main/res/drawable/ic_launcher_background.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="108dp"
+    android:height="108dp"
+    android:viewportWidth="108"
+    android:viewportHeight="108">
+    <path
+        android:fillColor="@color/ic_launcher_background"
+        android:pathData="M0,0h108v108h-108z" />
+</vector>

app/src/main/res/drawable/ic_launcher_foreground.xml

@@ -0,0 +1,14 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="108dp"
+    android:height="108dp"
+    android:viewportWidth="108"
+    android:viewportHeight="108">
+  <group android:scaleX="0.061"
+      android:scaleY="0.061"
+      android:translateX="21.06"
+      android:translateY="21.06">
+    <path
+        android:pathData="M480.859,520.767C486.88,504.294 483.548,489.658 473.18,476.663C451.429,449.4 429.349,422.4 407.406,395.29C370.115,349.215 332.857,303.113 295.504,257.088C289.433,249.607 286.667,241.349 288.655,231.887C291.203,219.755 301.661,211.145 314.474,211.122C377.739,211 441.006,210.872 504.27,211.25C519.537,211.341 531.854,218.846 541.463,230.737C578.15,276.134 614.877,321.499 651.591,366.874C674.322,394.968 697.004,423.1 719.804,451.138C745.329,482.526 745.544,526.965 719.577,561.007C698.98,588.011 677.793,614.566 656.783,641.254C619.791,688.242 582.734,735.179 545.705,782.138C545.481,782.422 545.252,782.704 545.058,783.008C530.88,805.232 510.818,813.54 484.414,812.973C428.043,811.763 371.628,812.573 315.231,812.615C308.17,812.621 301.574,811.212 295.753,807.12C282.386,797.721 280.036,780.463 290.691,765.962C299.673,753.736 309.315,741.993 318.702,730.065C370.103,664.748 421.516,599.44 472.922,534.126C476.065,530.134 478.821,525.907 480.859,520.767Z"
+        android:fillColor="@color/splash_logo_color"/>
+  </group>
+</vector>

app/src/main/res/mipmap-anydpi-v26/ic_launcher.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@drawable/ic_launcher_background" />
+    <foreground android:drawable="@drawable/ic_launcher_foreground" />
+    <monochrome android:drawable="@drawable/ic_launcher_foreground" />
+</adaptive-icon>

app/src/main/res/mipmap-anydpi-v26/ic_launcher_round.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+    <background android:drawable="@drawable/ic_launcher_background" />
+    <foreground android:drawable="@drawable/ic_launcher_foreground" />
+    <monochrome android:drawable="@drawable/ic_launcher_foreground" />
+</adaptive-icon>