Touch interface for phones and tablets; category toolbar for mouse and touch

- touch.rs: gesture recognition (tap, double tap, long press, drag, two-finger pan/pinch/rotate)
- Touch mode: Auto (touch device or first touch) / On / Off in Settings -> Game
- Larger interface factor on touch screens, top bar wraps, smaller minimap, fewer messages
- Toolbar grouped into categories with pop-up rows and a menu button, also on the desktop
- Long press shows information or drops held units; double tap with the hand slaps
- Savegame name via the browser's text dialog when the name field is tapped
- Touch help texts (EN/DE)

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

lang/en.lang

@@ -366,3 +366,21 @@ cloud.err_rate = Too many requests - please wait a moment.
 cloud.err_full = The savegame server is full.
 cloud.err_missing = This savegame no longer exists.
 cloud.err = The savegame server reported an error.
+
+# touch interface
+set.touch_ui = Touch interface
+val.auto_state = Auto ({0})
+cat.dig = Dig
+cat.hand = Hand
+cat.rooms = Rooms
+cat.towers = Towers
+cat.spells = Spells
+cat.orders = Orders
+cat.menu = Menu
+help.t_tap = Tap: use the tool (hand: pick up a unit; spells, flag, towers: at that spot)
+help.t_drag = Drag: dig, rooms and sell mark a rectangle; with other tools it moves the map
+help.t_two = Two fingers: move the map, pinch to zoom, twist to rotate the camera
+help.t_long = Long press: information about the spot; hand: drop the units there
+help.t_double = Double tap with the hand: backhand own units, punch heroes on your ground
+help.t_tools = Toolbar: categories open a row of tools; the menu button opens the pause menu
+help.start_touch = Tap to start