Add Android build target and responsive/drawer UI for phones and tablets

Restructure src-tauri into lib+bin (Tauri 2's mobile requirement — Android
embeds the app as a JNI cdylib, which needs a [lib] target with
tauri::mobile_entry_point) and scaffold gen/android/ via `cargo tauri
android init`. Builds and packages cleanly to a debug APK/AAB.

pcd_viewer.html: the 284px docked sidebar becomes a slide-in drawer under
768px viewport width (toggled from the rail, closes on backdrop tap), the
rail sheds its subtitle and secondary telemetry chips under 480px, and the
camera panel caps its width to the viewport. Also disables native pinch-zoom
(the canvas has its own via OrbitControls) and sets overscroll-behavior:none
for a full-bleed touch surface.

src-tauri/gen/android/gradle.properties

@@ -0,0 +1,24 @@
+# Project-wide Gradle settings.
+# IDE (e.g. Android Studio) users:
+# Gradle settings configured through the IDE *will override*
+# any settings specified in this file.
+# For more details on how to configure your build environment visit
+# http://www.gradle.org/docs/current/userguide/build_environment.html
+# Specifies the JVM arguments used for the daemon process.
+# The setting is particularly useful for tweaking memory settings.
+org.gradle.jvmargs=-Xmx2048m -Dfile.encoding=UTF-8
+# When configured, Gradle will run in incubating parallel mode.
+# This option should only be used with decoupled projects. More details, visit
+# http://www.gradle.org/docs/current/userguide/multi_project_builds.html#sec:decoupled_projects
+# org.gradle.parallel=true
+# AndroidX package structure to make it clearer which packages are bundled with the
+# Android operating system, and which are packaged with your app"s APK
+# https://developer.android.com/topic/libraries/support-library/androidx-rn
+android.useAndroidX=true
+# Kotlin code style for this project: "official" or "obsolete":
+kotlin.code.style=official
+# Enables namespacing of each library's R class so that its R class includes only the
+# resources declared in the library itself and none from the library's dependencies,
+# thereby reducing the size of the R class for that library
+android.nonTransitiveRClass=true
+android.nonFinalResIds=false