Integrate SimbaKit PetKit service into Docker stack and LangChain agent

Adds simbakit/ as a subfolder service that polls PetKit smart devices
(litter box, fountain, feeder) and exposes pet weight, litter activity,
and device health data via three new LangChain tools.

Also fixes stale alerts bug where cleared conditions (e.g. waste bin
full) persisted because the query used max alert time instead of the
device's last_seen_at timestamp.

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

.env.example

@@ -113,6 +113,15 @@ GOOGLE_CALENDAR_ENABLED=true
 # The file is mounted into the container at /app/config/gws-credentials.json
 GOOGLE_WORKSPACE_CLI_CREDENTIALS_FILE=/app/config/gws-credentials.json
 
+# SimbaKit / PetKit Configuration
+# PetKit account credentials (used by SimbaKit to poll device data)
+PETKIT_USERNAME=your-petkit-email
+PETKIT_PASSWORD=your-petkit-password
+PETKIT_REGION=US
+PETKIT_TIMEZONE=America/New_York
+# Internal URL for SimbaKit service (Docker network)
+SIMBAKIT_URL=http://simbakit:8585
+
 # Obsidian Configuration (headless sync)
 # Obsidian account credentials (used for `ob login` on container startup)
 OBSIDIAN_EMAIL=your-obsidian-email