feat: add Kestrelli faction ships and update related assets

- Add ship definitions for Kestrelli faction (scout, colonyship, transport,
  frigate, destroyer, cruiser, battleship) to artwork configuration
- Update character sprite (char-kestralli.png) and video (char-kestrelli.mp4)
- Update ships sprite sheet and PSD source file

data/mastervega-artwork.json

@@ -27,7 +27,15 @@
       "cruiser":    { "key": "vega-ship-human-cruiser",    "path": "assets/videos/vega/ship-human-cruiser.mp4" },
       "battleship": { "key": "vega-ship-human-battleship", "path": "assets/videos/vega/ship-human-battleship.mp4" }
     },
-    "kestrelli": null,
+    "kestrelli": {
+      "scout":      { "key": "vega-ship-kestrelli-scout",      "path": "assets/videos/vega/ship-kestrelli-scout.mp4" },
+      "colonyship": { "key": "vega-ship-kestrelli-colonyship", "path": "assets/videos/vega/ship-kestrelli-colony.mp4" },
+      "transport":  { "key": "vega-ship-kestrelli-transport",  "path": "assets/videos/vega/ship-kestrelli-transport.mp4" },
+      "frigate":    { "key": "vega-ship-kestrelli-frigate",    "path": "assets/videos/vega/ship-kestrelli-frigate.mp4" },
+      "destroyer":  { "key": "vega-ship-kestrelli-destroyer",  "path": "assets/videos/vega/ship-kestrelli-destroyer.mp4" },
+      "cruiser":    { "key": "vega-ship-kestrelli-cruiser",    "path": "assets/videos/vega/ship-kestrelli-cruiser.mp4" },
+      "battleship": { "key": "vega-ship-kestrelli-battleship", "path": "assets/videos/vega/ship-kestrelli-battleship.mp4" }
+    },
     "ursaal":    null,
     "umbrix":    null,
     "kkrix":     null,