Add tier-based scan scheduler and webhook triggers (FRE-4498)

- ScanScheduler: tier-based scheduling (BASIC=24h, PLUS=6h, PREMIUM=1h)
- WebhookHandler: HMAC-verified webhook ingestion with SCAN_TRIGGER support
- API routes: /scheduler and /webhooks endpoints under /api/v1/darkwatch
- Jobs: scheduled scan checker + webhook retry processor via BullMQ
- Schema: ScanSchedule, WebhookEvent models; ScanJob.scheduledBy field
- Types: ScheduleStatus, WebhookEventType, WebhookTriggerInput
- Tests: scheduler lifecycle + webhook signature/processing tests

Co-Authored-By: Paperclip <noreply@paperclip.ing>

services/spamshield/Dockerfile

@@ -0,0 +1,44 @@
+FROM node:20-alpine AS builder
+
+WORKDIR /app
+
+COPY package.json package-lock.json turbo.json ./
+COPY packages/api/package.json ./packages/api/
+COPY packages/db/package.json ./packages/db/
+COPY packages/types/package.json ./packages/types/
+COPY packages/core/package.json ./packages/core/ 2>/dev/null || true
+COPY packages/jobs/package.json ./packages/jobs/
+COPY packages/shared-notifications/package.json ./packages/shared-notifications/
+COPY services/darkwatch/package.json ./services/darkwatch/
+COPY services/spamshield/package.json ./services/spamshield/
+COPY services/voiceprint/package.json ./services/voiceprint/
+
+RUN npm ci
+
+COPY tsconfig.json ./
+COPY packages/types/tsconfig.json ./packages/types/
+COPY packages/db/tsconfig.json ./packages/db/
+COPY services/spamshield/tsconfig.json ./services/spamshield/
+COPY services/spamshield/ ./services/spamshield/
+COPY packages/types/ ./packages/types/
+COPY packages/db/ ./packages/db/
+
+RUN npm run build --workspace=@shieldai/types --workspace=@shieldai/db --workspace=@shieldai/spamshield
+
+FROM node:20-alpine AS runner
+
+WORKDIR /app
+
+RUN addgroup --system --gid 1001 nodejs && \
+    adduser --system --uid 1001 shieldai
+
+COPY --from=builder --chown=shieldai:nodejs /app/services/spamshield/dist ./dist
+COPY --from=builder --chown=shieldai:nodejs /app/node_modules ./node_modules
+COPY --from=builder --chown=shieldai:nodejs /app/services/spamshield/package.json ./package.json
+COPY --from=builder --chown=shieldai:nodejs /app/packages/db ./packages/db
+
+USER shieldai
+
+EXPOSE 3002
+
+CMD ["node", "dist/index.js"]