feat(03-01): add storage and thumbnail utilities

- Add storage.ts with directory management and file I/O
- Add thumbnails.ts with EXIF-aware thumbnail generation
- Thumbnails always output as JPEG with 80% quality

src/lib/server/images/storage.ts

@@ -0,0 +1,61 @@
+import { mkdir, writeFile, unlink } from 'node:fs/promises';
+import { join } from 'node:path';
+
+export const UPLOAD_DIR = 'data/uploads';
+export const ORIGINALS_DIR = 'data/uploads/originals';
+export const THUMBNAILS_DIR = 'data/uploads/thumbnails';
+
+/**
+ * Ensure upload directories exist
+ */
+export async function ensureDirectories(): Promise<void> {
+	await mkdir(ORIGINALS_DIR, { recursive: true });
+	await mkdir(THUMBNAILS_DIR, { recursive: true });
+}
+
+/**
+ * Save original image to filesystem
+ */
+export async function saveOriginal(id: string, ext: string, buffer: Buffer): Promise<void> {
+	const path = getOriginalPath(id, ext);
+	await writeFile(path, buffer);
+}
+
+/**
+ * Save thumbnail to filesystem (always jpg)
+ */
+export async function saveThumbnail(id: string, buffer: Buffer): Promise<void> {
+	const path = getThumbnailPath(id);
+	await writeFile(path, buffer);
+}
+
+/**
+ * Get path to original image
+ */
+export function getOriginalPath(id: string, ext: string): string {
+	return join(ORIGINALS_DIR, `${id}.${ext}`);
+}
+
+/**
+ * Get path to thumbnail (always jpg)
+ */
+export function getThumbnailPath(id: string): string {
+	return join(THUMBNAILS_DIR, `${id}.jpg`);
+}
+
+/**
+ * Delete both original and thumbnail files
+ * Does not throw if files don't exist
+ */
+export async function deleteImage(id: string, ext: string): Promise<void> {
+	try {
+		await unlink(getOriginalPath(id, ext));
+	} catch {
+		// File may not exist, ignore
+	}
+	try {
+		await unlink(getThumbnailPath(id));
+	} catch {
+		// File may not exist, ignore
+	}
+}