feat(ui): F8-11 — battles table under table submenu (#54)

Adds a sortable battles list as a new entity under the existing
`view → table` submenu (entity slug `battles`), replacing the
standalone top-level `battle log` shortcut which always opened a
"battle not found" placeholder. The single-battle viewer stays put
and is reached only by clicking a row (or a battle marker on the
map), identical to the existing `section-battles.svelte` flow.

Columns are planet (via the shared `planetLabel` helper) and shots
(the per-battle action count carried by `BattleSummary`), sortable
both ways with shots-desc default. No backend / FBS / map changes:
the wire payload is unchanged. Participants / observers / total
mass require the full BattleReport and were intentionally dropped
to avoid N round trips per menu open.

The top-level `battle log` item is removed from `header/view-menu`
and `sidebar/bottom-tabs` (and their stale comment blocks updated);
the now-orphan `game.view.battle` i18n key is dropped from both
locales.

ui/frontend/tests/game-shell-header.test.ts

@@ -147,7 +147,6 @@ describe("game-shell header", () => {
 		const destinations: Array<[string, string]> = [
 			["view-menu-item-map", "map"],
 			["view-menu-item-report", "report"],
-			["view-menu-item-battle", "battle"],
 			["view-menu-item-mail", "mail"],
 			["view-menu-item-designer-science", "designer-science"],
 		];
@@ -170,6 +169,7 @@ describe("game-shell header", () => {
 			["view-menu-item-table-fleets", "fleets"],
 			["view-menu-item-table-sciences", "sciences"],
 			["view-menu-item-table-races", "races"],
+			["view-menu-item-table-battles", "battles"],
 		];
 		for (const [testId, entity] of tableEntities) {
 			await fireEvent.click(ui.getByTestId("view-menu-trigger"));