Integrate Mealie meal planning service into LangChain agent

Wires up the existing MealieService to the conversational agent with tools
for querying today's meals, weekly meal plans, full recipes, shopping lists,
and creating new meal plan entries. Adds env vars to docker-compose and
updates the system prompt so the agent knows when to use each tool.

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

docker-compose.yml

@@ -45,6 +45,8 @@ services:
       - TAVILY_API_KEY=${TAVILIY_API_KEY}
       - YNAB_ACCESS_TOKEN=${YNAB_ACCESS_TOKEN}
       - YNAB_BUDGET_ID=${YNAB_BUDGET_ID}
+      - MEALIE_BASE_URL=${MEALIE_BASE_URL}
+      - MEALIE_API_TOKEN=${MEALIE_API_TOKEN}
       - TWILIO_ACCOUNT_SID=${TWILIO_ACCOUNT_SID}
       - TWILIO_AUTH_TOKEN=${TWILIO_AUTH_TOKEN}
       - TWILIO_WHATSAPP_NUMBER=${TWILIO_WHATSAPP_NUMBER}