refactor: rename frontend/ to web-player/ and format with prettier

Updates the compose build context, the Dockerfile header, the package
name and the docs. The compose service and container keep the name
frontend/musify-frontend, since nginx routes to http://frontend:3000.

The source files also carry the first prettier pass, so the rename and
the reformat land together for them.

web-player/src/routes/(app)/upload/+page.server.ts

@@ -0,0 +1,86 @@
+import type { Actions, PageServerLoad } from './$types';
+import { fail } from '@sveltejs/kit';
+import {
+	createApiClient,
+	requireAccessTokenAction,
+	requireUser,
+	unwrapOrFail
+} from '$lib/server/api';
+import { putPresigned, extOf, contentTypeOf, AUDIO_TYPES, IMAGE_TYPES } from '$lib/server/upload';
+
+const MAX_TITLE = 100;
+
+export const load: PageServerLoad = ({ locals, url }) => {
+	requireUser(locals, url);
+};
+
+export const actions: Actions = {
+	default: async ({ request, locals, fetch }) => {
+		const accessToken = requireAccessTokenAction(locals, 'Inicia sesión para subir música.');
+		if (typeof accessToken !== 'string') return accessToken;
+
+		const form = await request.formData();
+		const title = String(form.get('title') ?? '').trim();
+		const audio = form.get('audio');
+		const cover = form.get('cover');
+
+		if (title === '' || title.length > MAX_TITLE) {
+			return fail(400, { message: 'El título es obligatorio (máx. 100 caracteres).' });
+		}
+		if (!(audio instanceof File) || audio.size === 0) {
+			return fail(400, { message: 'Selecciona un archivo de audio.' });
+		}
+		if (!(cover instanceof File) || cover.size === 0) {
+			return fail(400, { message: 'Selecciona una portada.' });
+		}
+
+		const audioContentType = contentTypeOf(audio, AUDIO_TYPES);
+		const pictureContentType = contentTypeOf(cover, IMAGE_TYPES);
+		const api = createApiClient({ fetch, accessToken });
+
+		const urlsResult = await api.POST('/tracks/upload-urls', {
+			body: {
+				pictureFileType: extOf(cover.name) || 'jpg',
+				pictureContentType,
+				audioFileType: extOf(audio.name) || 'mp3',
+				audioContentType,
+				expectedPictureSizeBytes: cover.size,
+				expectedAudioSizeBytes: audio.size
+			}
+		});
+
+		const urlsFailure = unwrapOrFail(urlsResult, 'No se pudieron reservar las URLs de subida.');
+		if (urlsFailure) return urlsFailure;
+		const urls = urlsResult.data!;
+
+		try {
+			const [audioBuffer, coverBuffer] = await Promise.all([
+				audio.arrayBuffer(),
+				cover.arrayBuffer()
+			]);
+			await Promise.all([
+				putPresigned(urls.audioUploadUrl, Buffer.from(audioBuffer), urls.audioContentType),
+				putPresigned(urls.pictureUploadUrl, Buffer.from(coverBuffer), urls.pictureContentType)
+			]);
+		} catch (err) {
+			return fail(502, {
+				message: 'Falló la subida del archivo al almacenamiento.',
+				detail: err instanceof Error ? err.message : undefined
+			});
+		}
+
+		const trackResult = await api.POST('/tracks', {
+			body: {
+				title,
+				pictureIntentId: urls.pictureIntentId,
+				audioIntentId: urls.audioIntentId
+			}
+		});
+
+		const trackFailure = unwrapOrFail(trackResult, 'No se pudo crear la pista tras la subida.');
+		if (trackFailure) return trackFailure;
+		const track = trackResult.data!;
+
+		return { success: true, trackId: track.id, title: track.title };
+	}
+};