fix(lint): resolve all biome warnings across API, web, and image-engine

API:
- Replace string concatenation with template literals (batch, pipeline,
  tool-factory, content-aware-resize, passport-photo, remove-background)
- Remove unused imports (teams, color-adjustments, image-enhancement)
- Replace non-null assertions with guard clauses in bg-effects and stitch
- Use optional chaining in docs route

Image-engine:
- Remove unused OutputFormat imports (compress, convert)
- Use local variables instead of reassigning parameters (optimize-for-web, sharpen)

Web:
- Fix useExhaustiveDependencies: remove genuinely redundant deps, add
  biome-ignore comments for intentional patterns (src prop, cleanup fns)
- Replace non-null assertions with null-safe alternatives
- Add accessible titles to inline SVGs (color-settings, image-enhancement-settings)
- Fix noLabelWithoutControl: associate labels via htmlFor/id or use <span>
  (image-to-base64-settings, edit-metadata-settings, qr-generate-settings)
- Replace div[role="button"] with <button> (pdf-to-image-settings)
- Use stable keys instead of array indices (collage-preview, collage-settings)
- Fix noStaticElementInteractions in collage-preview (role="none")
- Remove unused function parameters and imports

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

@@ -1,5 +1,5 @@
 import sharp from "sharp";
-import type { CompressOptions, OutputFormat, Sharp } from "../types.js";
+import type { CompressOptions, Sharp } from "../types.js";
 
 const FORMAT_MAP: Record<string, string> = {
   jpg: "jpeg",

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

@@ -1,4 +1,4 @@
-import type { ConvertOptions, OutputFormat, Sharp } from "../types.js";
+import type { ConvertOptions, Sharp } from "../types.js";
 
 /**
  * Maps user-facing format names to Sharp format strings.

packages/image-engine/src/operations/optimize-for-web.ts

@@ -10,9 +10,11 @@ export async function optimizeForWeb(image: Sharp, options: OptimizeForWebOption
     stripMetadata = true,
   } = options;
 
+  let pipeline = image;
+
   // Step 1: Resize if max dimensions are set
   if (maxWidth || maxHeight) {
-    image = image.resize({
+    pipeline = pipeline.resize({
       width: maxWidth,
       height: maxHeight,
       fit: "inside",
@@ -24,19 +26,19 @@ export async function optimizeForWeb(image: Sharp, options: OptimizeForWebOption
   // Sharp strips metadata by default on output, so we only need to act
   // when the user wants to KEEP metadata.
   if (!stripMetadata) {
-    image = image.withMetadata();
+    pipeline = pipeline.withMetadata();
   }
 
   // Step 3: Convert to target format with optimized settings
   switch (format) {
     case "webp":
-      return image.webp({ quality, effort: 4 });
+      return pipeline.webp({ quality, effort: 4 });
     case "jpeg":
-      return image.jpeg({ quality, progressive, mozjpeg: true });
+      return pipeline.jpeg({ quality, progressive, mozjpeg: true });
     case "avif":
-      return image.avif({ quality, effort: 4 });
+      return pipeline.avif({ quality, effort: 4 });
     case "png":
-      return image.png({ compressionLevel: 9, palette: true });
+      return pipeline.png({ compressionLevel: 9, palette: true });
     default:
       throw new Error(`Unsupported format: ${format}`);
   }

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

@@ -27,20 +27,21 @@ export async function sharpenAdvanced(
   const { method, denoise } = options;
 
   // Optional noise reduction pre-pass
+  let pipeline = image;
   if (denoise && denoise !== "off") {
     const kernelSize = DENOISE_KERNEL[denoise];
     if (kernelSize) {
-      image = image.median(kernelSize);
+      pipeline = pipeline.median(kernelSize);
     }
   }
 
   switch (method) {
     case "adaptive":
-      return sharpenAdaptive(image, options);
+      return sharpenAdaptive(pipeline, options);
     case "unsharp-mask":
-      return sharpenUnsharpMask(image, options);
+      return sharpenUnsharpMask(pipeline, options);
     case "high-pass":
-      return sharpenHighPass(image, options);
+      return sharpenHighPass(pipeline, options);
     default:
       throw new Error(`Unknown sharpening method: ${method}`);
   }