feat(agiliton-account): Phase 1 service scaffold

TypeScript + Fastify service implementing:
- Google + Microsoft SSO (POST /v1/auth/sso/{google,microsoft})
- JWT issuance + LiteLLM virtual key provisioning on first login
- AES-256-GCM encrypted virtual key storage in Postgres
- Conversation CRUD (GET/POST/DELETE /v1/conversations, /messages)
- GDPR export + soft-delete (/v1/me/export, /v1/me/delete)
- WebSocket MCP bridge (/v1/mcp-bridge) with JWT auth
- MCP demux endpoint (/mcp/demux/:customer_id/mcp) for LiteLLM tool routing
- DB migration script creating sb_customers, sb_conversations, sb_messages
- 9 unit tests (bridge + crypto), all passing
- Dockerfile + docker-compose targeting port 4100

CF-3032

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -0,0 +1,23 @@
+FROM node:22-alpine AS builder
+
+WORKDIR /app
+COPY package*.json ./
+RUN npm ci
+COPY tsconfig.json ./
+COPY src ./src
+RUN npm run build
+
+FROM node:22-alpine AS runtime
+
+WORKDIR /app
+COPY package*.json ./
+RUN npm ci --omit=dev
+COPY --from=builder /app/dist ./dist
+
+ENV NODE_ENV=production
+EXPOSE 4100
+
+HEALTHCHECK --interval=30s --timeout=5s --start-period=10s \
+  CMD wget -qO- http://localhost:4100/health || exit 1
+
+CMD ["node", "dist/index.js"]