Make player character color and icon optional

Clicking an already-selected color or icon in the create/edit form now
deselects it. PCs without a color use the default combatant styling;
PCs without an icon show no icon. Domain, application, persistence,
and display layers all updated to handle the optional fields.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/web/src/components/action-bar.tsx

@@ -95,9 +95,12 @@ function AddModeSuggestions({
 						</div>
 						<ul>
 							{pcMatches.map((pc) => {
-								const PcIcon = PLAYER_ICON_MAP[pc.icon as PlayerIcon];
-								const pcColor =
-									PLAYER_COLOR_HEX[pc.color as keyof typeof PLAYER_COLOR_HEX];
+								const PcIcon = pc.icon
+									? PLAYER_ICON_MAP[pc.icon as PlayerIcon]
+									: undefined;
+								const pcColor = pc.color
+									? PLAYER_COLOR_HEX[pc.color as keyof typeof PLAYER_COLOR_HEX]
+									: undefined;
 								return (
 									<li key={pc.id}>
 										<button