Wire Firefly III and importer into Traefik

Add traefik_proxy network and labels for firefly.jbnel.dev and
import.jbnel.dev with Let's Encrypt TLS. Fix cron to use alpine
with proper crond loop instead of one-shot. Add STATIC_CRON_TOKEN.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.env.example

@@ -46,3 +46,7 @@ MAIL_FROM=firefly@jbnel.dev
 FIREFLY_III_URL=http://app:8080
 VANITY_URL=https://import.jbnel.dev
 FIREFLY_III_ACCESS_TOKEN=REPLACE_AFTER_FIRST_RUN
+
+# --- Cron ---
+# Generate with: python3 -c "import secrets; print(secrets.token_hex(16))"
+STATIC_CRON_TOKEN=REPLACE_WITH_RANDOM_HEX