Add Firefly III compose stack with k8s migration scaffold

PostgreSQL 16, Redis 7, Firefly III core + data importer, cron container.
Health checks on all services. .env.example documents all variables.
k8s/ directory scaffolded for future migration.

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

.env.example

@@ -0,0 +1,48 @@
+# -------------------------------------------------------
+# Firefly III — environment configuration
+# Copy to .env and fill in values before starting.
+# -------------------------------------------------------
+
+# --- App ---
+APP_ENV=production
+APP_DEBUG=false
+APP_KEY=base64:REPLACE_WITH_GENERATED_KEY
+APP_URL=https://firefly.jbnel.dev
+TRUSTED_PROXIES=**
+
+# --- Database (PostgreSQL) ---
+DB_CONNECTION=pgsql
+DB_HOST=db
+DB_PORT=5432
+DB_DATABASE=firefly
+DB_USERNAME=firefly
+DB_PASSWORD=REPLACE_WITH_STRONG_PASSWORD
+
+# Required by the postgres container
+POSTGRES_DB=firefly
+POSTGRES_USER=firefly
+POSTGRES_PASSWORD=REPLACE_WITH_STRONG_PASSWORD
+
+# --- Redis ---
+REDIS_HOST=redis
+REDIS_PORT=6379
+REDIS_PASSWORD=REPLACE_WITH_STRONG_PASSWORD
+
+# --- Cache / Sessions ---
+CACHE_DRIVER=redis
+SESSION_DRIVER=redis
+
+# --- Mail (optional) ---
+MAIL_MAILER=log
+MAIL_HOST=
+MAIL_PORT=
+MAIL_USERNAME=
+MAIL_PASSWORD=
+MAIL_ENCRYPTION=
+MAIL_FROM=firefly@jbnel.dev
+
+# --- Data Importer ---
+# Set after Firefly III is running and you've created a Personal Access Token
+FIREFLY_III_URL=http://app:8080
+VANITY_URL=https://import.jbnel.dev
+FIREFLY_III_ACCESS_TOKEN=REPLACE_AFTER_FIRST_RUN