fix: QA sweep -- SSE crash, memory leaks, HEIC Docker decode, TGA detection, lint cleanup

- Fix SSE write-after-end crash in progress.ts (remove callback before ending stream)
- Fix blob URL memory leaks: revoke processedPreviewUrl and old HEIC preview URLs
- Add AbortController to batch fetch in use-tool-processor and use-pipeline-processor
- Fix TGA format misidentified as CUR (extension overrides magic bytes)
- Add libheif-plugin-libde265 to Docker for HEIC/HEIF decode support
- Remove unused imports and state (AppLayout, setSampledColor, useEffect)
- Fix non-null assertions in meme-text-renderer and meme-generator
- Fix confusing void type in meme-templates
- Remove unnecessary useEffect deps in adjustments-panel
- Fix Playwright strict mode violations in 5 E2E tests

tests/e2e/gui-performance.spec.ts

@@ -554,8 +554,8 @@ test.describe("File Upload Preview Timing", () => {
     await expect(
       page
         .getByText(/test-image/i)
-        .first()
-        .or(page.locator("img[src^='blob:']").first()),
+        .or(page.locator("img[src^='blob:']"))
+        .first(),
     ).toBeVisible({ timeout: 5_000 });
     const previewTime = Date.now() - start;