Added pause functionality for private multiplayer games (#2657)

If this PR fixes an issue, link it below. If not, delete these two
lines.
Resolves #2491

## Description:
Adds pause/unpause functionality for private multiplayer games. Only the
lobby creator can pause the game, and all players see a pause overlay
when the game is paused.

  **Key features:**
- Lobby creator sees pause/play button in control panel (alongside
existing singleplayer/replay controls)
  - Server validates that only lobby creator can toggle pause
  - All players see "Game paused by Lobby Creator" overlay when paused
  - Game state freezes (no turn execution) while paused
  - Unpause resumes normal gameplay

  **Implementation details:**
- Server-side pause state (`isPaused`) prevents turn execution during
pause
- Each client receives `isLobbyCreator` flag in `GameStartInfo` to
show/hide pause button
- Added `TogglePauseIntent` that broadcasts to all clients via
`NoOpExecution`
  - New `PauseOverlay` component (shows in single player also)

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

furo18

<img width="1459" height="861" alt="Screenshot 2025-12-20 at 15 16 33"
src="https://github.com/user-attachments/assets/f5a3222f-f54b-473c-b0f6-104ce4c1e7a8"
/>

resources/lang/en.json

@@ -744,6 +744,10 @@
     "choose_spawn": "Choose a starting location",
     "random_spawn": "Random spawn is enabled. Selecting starting location for you..."
   },
+  "pause": {
+    "singleplayer_game_paused": "Game paused",
+    "multiplayer_game_paused": "Game paused by Lobby Creator"
+  },
   "territory_patterns": {
     "title": "Skins",
     "colors": "Colors",