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/index.ts

@@ -1,7 +1,7 @@
 import { randomUUID } from "node:crypto";
 import cors from "@fastify/cors";
 import rateLimit from "@fastify/rate-limit";
-import { isGpuAvailable } from "@snapotter/ai";
+import { getDispatcherStatus, isGpuAvailable } from "@snapotter/ai";
 import { APP_VERSION } from "@snapotter/shared";
 import { eq } from "drizzle-orm";
 import Fastify from "fastify";
@@ -222,7 +222,7 @@ app.get("/api/v1/admin/health", async (request, reply) => {
     storage: { mode: env.STORAGE_MODE, available: "N/A" },
     database: dbOk ? "ok" : "error",
     queue: { active: 0, pending: 0 },
-    ai: { gpu: isGpuAvailable() },
+    ai: { gpu: isGpuAvailable(), dispatcher: getDispatcherStatus() },
   };
 });