fix(sharing): make public note colors follow the visitor's theme

The public share page picked the note background from the light palette
unconditionally, while app.html applies data-theme="dark" on every page.
A visitor in dark mode therefore got a light pastel card rendered with the
dark theme's light text colour — washed out and barely readable.

Emit both palettes as custom properties and let [data-theme] select one, so
the correct colour lands on the first paint of this SSR page instead of
flashing after hydration.

Reported by a user over email.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/routes/(share)/s/[token]/+page.svelte

@@ -1,5 +1,5 @@
 <script lang="ts">
-	import { NOTE_COLORS } from '$lib/utils/colors.js';
+	import { getNoteColor } from '$lib/utils/colors.js';
 	import { renderMarkdown } from '$lib/utils/markdown.js';
 	import { linkifyText } from '$lib/utils/checklist.js';
 	import type { NoteColor, PublicAttachment } from '$lib/types/index.js';
@@ -12,8 +12,12 @@
 
 	const { data } = $props();
 
+	// Both palettes are emitted as custom properties so the card follows the visitor's theme on the
+	// first paint — the CSS variables in app.css switch on [data-theme], which app.html sets before
+	// hydration, so a JS-resolved single colour would flash the wrong palette on this SSR page.
 	const noteColor = data.color as NoteColor;
-	const bgColor = NOTE_COLORS[noteColor]?.bg ?? NOTE_COLORS.default.bg;
+	const bgLight = getNoteColor(noteColor, false);
+	const bgDark = getNoteColor(noteColor, true);
 
 	const renderedContent = renderMarkdown(data.content);
 
@@ -55,8 +59,8 @@
 
 <div class="mx-4 w-full max-w-2xl py-10">
 	<article
-		class="rounded-sm border border-[var(--border-subtle)] shadow-[var(--card-shadow)] overflow-hidden"
-		style="background-color: {bgColor}"
+		class="note-surface rounded-sm border border-[var(--border-subtle)] shadow-[var(--card-shadow)] overflow-hidden"
+		style="--note-bg: {bgLight}; --note-bg-dark: {bgDark}"
 		data-testid="shared-note"
 	>
 		<div class="px-6 py-5">
@@ -128,3 +132,13 @@
 		</a>
 	</div>
 </div>
+
+<style>
+	.note-surface {
+		background-color: var(--note-bg);
+	}
+
+	:global([data-theme='dark']) .note-surface {
+		background-color: var(--note-bg-dark);
+	}
+</style>

tests/e2e/public-sharing.spec.ts

@@ -121,6 +121,54 @@ test.describe('Public Note Sharing', () => {
 		await expect(card.getByTestId('sharing-indicator')).toBeVisible();
 	});
 
+	test('Scenario: Shared note follows a dark-mode visitor theme', async ({
+		authenticatedPage: page,
+		browser
+	}) => {
+		// Given a publicly shared note colored "fog"
+		const note = await createNoteViaApi(page, 'Dark Visitor Note', 'Readable in dark mode');
+		await page.request.patch(`/api/notes/${note.id}`, { data: { color: 'fog' } });
+		const token = await createShareViaApi(page, note.id);
+
+		// When a visitor whose system prefers dark mode opens the share URL
+		const context = await browser.newContext({ colorScheme: 'dark' });
+		const publicPage = await context.newPage();
+		await publicPage.goto(`/s/${token}`);
+
+		// Then the note is rendered on the dark "fog" surface, so its text stays legible
+		await expect(publicPage.locator('html')).toHaveAttribute('data-theme', 'dark');
+		await expect(publicPage.getByTestId('shared-note')).toHaveCSS(
+			'background-color',
+			'rgb(34, 46, 58)'
+		);
+
+		await context.close();
+	});
+
+	test('Scenario: Shared note follows a light-mode visitor theme', async ({
+		authenticatedPage: page,
+		browser
+	}) => {
+		// Given a publicly shared note colored "fog"
+		const note = await createNoteViaApi(page, 'Light Visitor Note', 'Readable in light mode');
+		await page.request.patch(`/api/notes/${note.id}`, { data: { color: 'fog' } });
+		const token = await createShareViaApi(page, note.id);
+
+		// When a visitor whose system prefers light mode opens the share URL
+		const context = await browser.newContext({ colorScheme: 'light' });
+		const publicPage = await context.newPage();
+		await publicPage.goto(`/s/${token}`);
+
+		// Then the note is rendered on the light "fog" surface
+		await expect(publicPage.locator('html')).not.toHaveAttribute('data-theme', 'dark');
+		await expect(publicPage.getByTestId('shared-note')).toHaveCSS(
+			'background-color',
+			'rgb(212, 228, 237)'
+		);
+
+		await context.close();
+	});
+
 	test('Scenario: Copy link button copies to clipboard', async ({
 		authenticatedPage: page
 	}) => {