fix: format preservation, dispatcher stability, and health reporting

Closes #17, #18, #19, #31, #32, #33, #34

Format preservation (#17, #18, #19):
- Add resolveOutputFormat to rotate, resize, text-overlay, watermark-text,
  border, replace-color, blur-faces, upscale, erase-object, restore-photo
- Alpha-aware fallback: border with corner radius/shadow and replace-color
  with makeTransparent fall back to PNG for non-alpha formats (JPEG)
- Python sidecar tools (blur-faces, upscale, erase-object) now convert
  PNG output back to input format, matching restore-photo/colorize pattern
- Upscale and erase-object default to "auto" format detection instead of PNG

Dispatcher stability (#31, #32):
- Add gc.collect() and torch.cuda.empty_cache() after each dispatcher request
- Add configurable max_requests (default 50) for periodic dispatcher restart
- Add exponential backoff to dispatcher crash recovery in bridge.ts
- Circuit breaker: 5 crashes within 60s permanently disables dispatcher
- Reset crash counter on successful dispatcher startup

Health & security (#33, #34):
- Export getDispatcherStatus() from @snapotter/ai with running/ready/failed/
  gpu/pid/consecutiveCrashes fields
- Admin health endpoint now includes full dispatcher status
- Add pip-audit job to CI workflow for Python dependency scanning

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

@@ -1,6 +1,7 @@
 import type { FastifyInstance } from "fastify";
 import sharp from "sharp";
 import { z } from "zod";
+import { resolveOutputFormat } from "../../lib/output-format.js";
 import { createToolRoute } from "../tool-factory.js";
 
 const hexColor = z.string().regex(/^#[0-9a-fA-F]{6}$/);
@@ -144,9 +145,20 @@ export function registerBorder(app: FastifyInstance) {
           .toBuffer();
       }
 
-      const buffer = await sharp(buf).png().toBuffer();
-      const outName = filename.replace(/\.[^.]+$/, ".png");
-      return { buffer, filename: outName, contentType: "image/png" };
+      const outputFormat = await resolveOutputFormat(inputBuffer, filename);
+      const ALPHA_FORMATS = new Set(["png", "webp", "avif", "tiff"]);
+      const needsAlpha = settings.cornerRadius > 0 || settings.shadow;
+
+      if (needsAlpha && !ALPHA_FORMATS.has(outputFormat.format)) {
+        const buffer = await sharp(buf).png().toBuffer();
+        const outName = filename.replace(/\.[^.]+$/, ".png");
+        return { buffer, filename: outName, contentType: "image/png" };
+      }
+
+      const buffer = await sharp(buf)
+        .toFormat(outputFormat.format, { quality: outputFormat.quality })
+        .toBuffer();
+      return { buffer, filename, contentType: outputFormat.contentType };
     },
   });
 }