feat: add HEIC/HEIF format support for input and output

Add bidirectional HEIC support using system libheif CLI tools (heif-enc/heif-dec)
for HEVC encoding/decoding, since Sharp's bundled libheif only supports AV1.

- HEIC input: all tools now accept iPhone HEIC photos via heif-dec pre-processing
- HEIC output: convert tool produces true HEIC (HEVC) via heif-enc
- Docker: adds libheif-examples package for heif-enc/heif-dec CLI tools
- Tests: full conversion matrix (7x7), unit tests, and Playwright e2e tests
- Docs: updated OpenAPI spec, image-engine docs, getting-started, llms-full.txt

packages/image-engine/src/operations/compress.ts

@@ -1,7 +1,7 @@
 import sharp from "sharp";
 import type { CompressOptions, OutputFormat, Sharp } from "../types.js";
 
-const FORMAT_MAP: Record<OutputFormat, string> = {
+const FORMAT_MAP: Record<string, string> = {
   jpg: "jpeg",
   png: "png",
   webp: "webp",

packages/image-engine/src/operations/convert.ts

@@ -1,6 +1,11 @@
 import type { ConvertOptions, OutputFormat, Sharp } from "../types.js";
 
-const FORMAT_MAP: Record<OutputFormat, string> = {
+/**
+ * Maps user-facing format names to Sharp format strings.
+ * Note: HEIC is excluded because Sharp cannot encode HEVC.
+ * HEIC encoding is handled at the API route level via heif-enc.
+ */
+const FORMAT_MAP: Record<string, string> = {
   jpg: "jpeg",
   png: "png",
   webp: "webp",