Share icon packs between desktop and Android

The Android app's Material icons become a TeamSpeak-format pack shipped in
core, which the desktop offers next to the TeamSpeak packs. Android now
draws its icons from packs too and imports TeamSpeak's own zips, falling
back to the Material pack for what they lack.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

ts3-client/README.md

@@ -162,6 +162,11 @@ Android app in [`../android`](../android) does.
   TeamSpeak 3 client (`$TS3_CLIENT_DIR` or the usual install paths) and a folder of
   your choosing, so the official packs (`default_colored_2014.zip`,
   `default_mono_2014.zip`, the legacy `default.zip`) work unchanged.
+- **Material**, a pack in the same format built from Google's Material icons, ships
+  with the client (`core/src/main/resources/gfx/material`, generated by
+  `tools/material-icon-pack.py`). Its monochrome icons paint with `currentColor`, which
+  follows the theme's text colour. It is the Android app's default, and the Android app
+  draws TeamSpeak packs too — import one (e.g. `default_colored_2014.zip`) in its settings.
 - The pack draws the tree (server, channel, client state), the toolbar, the menus,
   the context menus, the file browser and TeamSpeak's default group icons. Vector
   art is rasterised at the size it is drawn at; a pack's `FALLBACK` option decides
@@ -240,8 +245,9 @@ core/   com.ts3client
 ├── contacts                 friends and blocked clients, in TS3's own record format
 ├── text                     BBCode, TeamSpeak links, chat search
 ├── gfx
-│   ├── IconPack             an icon pack zip/folder + its settings.ini mapping
-│   └── IconPacks            discovery of installed packs
+│   ├── IconPack             an icon pack zip/folder/classpath folder + its settings.ini mapping
+│   ├── IconPacks            discovery of installed packs, the shipped Material one, lookup order
+│   └── IconKeys             the icon keys the channel tree asks for
 ├── hotkey
 │   ├── HotkeyAction         catalogue of TeamSpeak's hotkey actions (RE'd from its binary)
 │   ├── Hotkey/HotkeyCombo   one binding: keys, trigger edge, server scope, argument