feat(ui): map canvas follows light/dark theme; fix invisible gear control

The map view now selects a DARK_THEME or LIGHT_THEME palette from the
resolved app theme and threads it through every primitive builder, so
the canvas, planets, ship groups, cargo routes, battle/bombing markers,
fog, reach + selection rings, pending-Send tracks, and the pick overlay
all switch with the rest of the chrome. A theme flip remounts the
renderer preserving the camera — Pixi bakes the background at init and
every primitive bakes its colour at build, so a live re-tint is not
possible on the same instance.

This also fixes the reported bug: the gear-popover trigger and the
loading overlay hardcoded a dark navy background, so in light theme the
gear was invisible (dark icon on dark chip) until hover flipped it to a
white chip. Both now use the --color-surface-overlay token and read
correctly in both themes.

The light palette mirrors the dark one role-for-role, darkened /
saturated for contrast on a light background while keeping the incoming,
battle, and bombing accents vivid. The values are a first pass meant to
be refined during the F8 manual-QA loop.

Removes the now-dead "Phase 35" references from the code and lifts the
map-recoloring prohibition from the design-system / renderer docs; the
battle scene stays a fixed-palette data-viz surface.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

ui/frontend/tests/selection-ring.test.ts

@@ -1,10 +1,7 @@
 import { describe, expect, it } from "vitest";
 
-import {
-	computeSelectionRing,
-	SELECTION_RING_COLOR,
-	SELECTION_RING_ID,
-} from "../src/map/selection-ring";
+import { computeSelectionRing, SELECTION_RING_ID } from "../src/map/selection-ring";
+import { DARK_THEME, LIGHT_THEME } from "../src/map/world";
 
 const planets = [
 	{ number: 1, x: 10, y: 20 },
@@ -29,8 +26,15 @@ describe("computeSelectionRing", () => {
 			y: 40,
 			hitSlopPx: 0,
 		});
-		expect(ring?.style.strokeColor).toBe(SELECTION_RING_COLOR);
+		// Defaults to the dark palette.
+		expect(ring?.style.strokeColor).toBe(DARK_THEME.selectionRing);
 		// Sits outside the planet marker (radius 6 world units).
 		expect(ring?.radius ?? 0).toBeGreaterThan(6);
 	});
+
+	it("uses the supplied palette's ring colour", () => {
+		const ring = computeSelectionRing(planets, 2, LIGHT_THEME);
+		expect(ring?.style.strokeColor).toBe(LIGHT_THEME.selectionRing);
+		expect(LIGHT_THEME.selectionRing).not.toBe(DARK_THEME.selectionRing);
+	});
 });