feat(setup): bootstrap Android plugin and web UI

This initial commit adds a multi-part scaffold for Wechselbild, including a web UI and an Android plugin.
It introduces frontend assets and a package.json-based dev setup, plus plugin scaffolding for Android with Kotlin sources and Cargo.toml for the Tauri plugin.

- Adds Android wallpaper plugin with Kotlin sources and manifest
- Includes web UI scaffold with index.html and package.json
- Adds Tauri plugin scaffold with Cargo.toml and build config

plugins/permissions/autogenerated/commands/select_images.toml

@@ -0,0 +1,13 @@
+# Automatically generated - DO NOT EDIT!
+
+"$schema" = "../../schemas/schema.json"
+
+[[permission]]
+identifier = "allow-select-images"
+description = "Enables the select_images command without any pre-configured scope."
+commands.allow = ["select_images"]
+
+[[permission]]
+identifier = "deny-select-images"
+description = "Denies the select_images command without any pre-configured scope."
+commands.deny = ["select_images"]