feat: embed Chatwoot live-chat widget (destek.sase.tr)

Site-wide live-chat widget served from the self-hosted Chatwoot at
destek.sase.tr, with verified user identity and vehicle context.

- apps/web: lib/chatwoot.ts loads the SDK lazily (mirrors the PostHog
  init pattern), init in main.tsx, identify logged-in users in __root
  via a server-computed HMAC, and attach the viewed vehicle (VIN/brand/
  model) as contact custom attributes on the vehicle detail page.
- apps/api: GET /api/chatwoot/identity (AuthGuard-protected) returns
  HMAC-SHA256(user.id) so the widget can use verified identity.
- env: VITE_CHATWOOT_BASE_URL + VITE_CHATWOOT_WEBSITE_TOKEN (build-time,
  wired through docker-compose.coolify.yml build args + Dockerfile ARG)
  and CHATWOOT_HMAC_TOKEN (api runtime). All optional — widget and
  endpoint no-op when unset.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docker-compose.coolify.yml

@@ -8,6 +8,8 @@ services:
         - VITE_FARO_COLLECTOR_URL=${VITE_FARO_COLLECTOR_URL:-}
         - VITE_POSTHOG_KEY=${VITE_POSTHOG_KEY:-}
         - VITE_META_PIXEL_ID=${VITE_META_PIXEL_ID:-}
+        - VITE_CHATWOOT_BASE_URL=${VITE_CHATWOOT_BASE_URL:-}
+        - VITE_CHATWOOT_WEBSITE_TOKEN=${VITE_CHATWOOT_WEBSITE_TOKEN:-}
     environment:
       - NODE_ENV=production
       - PORT=4000
@@ -64,6 +66,8 @@ services:
       - OTEL_SERVICE_NAME=${OTEL_SERVICE_NAME:-sase-api}
       - OTEL_TRACE_SAMPLE_RATE=${OTEL_TRACE_SAMPLE_RATE:-1.0}
       - ML_PREDICTION_ENABLED=${ML_PREDICTION_ENABLED:-false}
+      # Chatwoot live-chat widget — HMAC secret for verified user identity
+      - CHATWOOT_HMAC_TOKEN=${CHATWOOT_HMAC_TOKEN:-}
     depends_on:
       sase-redis:
         condition: service_healthy