fix: resolve 14 security, correctness, and robustness issues found during QA sweep

Security fixes:
- Add auth + ownership check to thumbnail endpoint (was unauthenticated)
- Validate ExifTool fieldsToRemove against safe tag name pattern
- Add SVG sanitization to pipeline execute and batch endpoints
- Replace basename() with sanitizeFilename() in 16 tool routes
- Escape SQL LIKE wildcards in file search to prevent pattern injection
- Improve settings HTML tag validation pattern

Bug fixes:
- Skip autoOrient for SVG inputs in pipeline (prevents misinterpretation)
- Remove double-encode in compress targetSize (was degrading quality)
- Fix bg-effects alpha value from 255 to 1.0 (Sharp expects float)
- Guard download stream error handler against headers-already-sent race
- Use O_EXCL atomic file creation for install lock (fixes TOCTOU race)
- Truncate collage file array to template image count

UX fixes:
- Accept empty JSON bodies on POST endpoints (install/uninstall)
- Custom JSON content type parser that treats empty body as {}

apps/api/src/routes/tools/stitch.ts

@@ -1,6 +1,6 @@
 import { randomUUID } from "node:crypto";
 import { writeFile } from "node:fs/promises";
-import { basename, join } from "node:path";
+import { join } from "node:path";
 import type { FastifyInstance } from "fastify";
 import sharp from "sharp";
 import { z } from "zod";
@@ -8,6 +8,7 @@ import { env } from "../../config.js";
 import { autoOrient } from "../../lib/auto-orient.js";
 import { formatZodErrors } from "../../lib/errors.js";
 import { validateImageBuffer } from "../../lib/file-validation.js";
+import { sanitizeFilename } from "../../lib/filename.js";
 import { ensureSharpCompat } from "../../lib/heic-converter.js";
 import { createWorkspace } from "../../lib/workspace.js";
 
@@ -58,7 +59,7 @@ export function registerStitch(app: FastifyInstance) {
           if (buf.length > 0) {
             files.push({
               buffer: buf,
-              filename: basename(part.filename ?? `image-${files.length}`),
+              filename: sanitizeFilename(part.filename ?? `image-${files.length}`),
             });
           }
         } else if (part.fieldname === "settings") {