perf: optimize Docker images - backend 294MB, gateway 1.89GB

Backend:
- node:22-alpine runtime (from 1.82GB to 294MB, 84% reduction)
- COPY --chown instead of chown -R layer
- pnpm install --prod after build for clean .pnpm store
- Pinned pnpm@10 to avoid v11 build-script lockout

Gateway:
- Fixed TypeScript errors (missing table defs in shared schema)
- Restored node-crc Rust patch for native compilation
- Multi-stage build with COPY --chown
- pnpm install --prod after build
- ffmpeg with --no-install-recommends

Proxy:
- Restructured for standalone build (build errors are pre-existing)

General:
- pnpm@10 in all builds (avoids ERR_PNPM_IGNORED_BUILDS)
- Clean .dockerignore (excludes docs/design/scripts)

services/discord-gateway/package.json

@@ -4,7 +4,20 @@
   "description": "Discord Gateway service - handles message capture, voice recording, and AI moderation",
   "type": "module",
   "main": "dist/index.js",
-  "packageManager": "pnpm@11.1.3",
+  "pnpm": {
+    "onlyBuiltDependencies": [
+      "@discordjs/opus",
+      "@lng2004/node-datachannel",
+      "esbuild",
+      "node-av",
+      "node-crc",
+      "sharp",
+      "zeromq"
+    ],
+    "patchedDependencies": {
+      "node-crc@4.0.0": "./patches/node-crc@4.0.0.patch"
+    }
+  },
   "scripts": {
     "dev": "tsx watch src/index.ts",
     "start": "node dist/index.js",