feat(env): load dotenv in entrypoint; add .env.example; stop tracking .env files

.env.example

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+# Copy this file to .env for local development. Do not commit your real .env.
+# Heroku: set these in Config Vars; dotenv is a no-op in production.
+
+# Discord bot
+TOKEN=
+MODE=Normal
+
+# Caching and sweepers
+CACHE_MESSAGES_LIMIT=50
+CACHE_MEMBERS_LIMIT=100
+SWEEP_MESSAGES_INTERVAL_SECONDS=300
+SWEEP_MESSAGES_LIFETIME_SECONDS=900
+
+# Logging and diagnostics
+LOG_LEVEL=info
+PRISMA_LOG_QUERIES=0
+MEMORY_LOG_INTERVAL_SECONDS=0
+ENABLE_MEMORY_OPTIMIZER=false
+
+# Redis connection
+REDIS_URL=
+REDIS_PASS=
+
+# Appwrite (for reminders)
+APPWRITE_ENDPOINT=
+APPWRITE_PROJECT_ID=
+APPWRITE_API_KEY=
+
+# Reminders
+REMINDERS_POLL_INTERVAL_SECONDS=30
+
+# Google AI / Gemini
+GOOGLE_AI_API_KEY=
+GEMINI_API_KEY=
+GENAI_IMAGE_MODEL=
+
+# Slash command registration context
+# Your Discord Application ID
+CLIENT=
+# Test guild ID (for per-guild command registration)
+guildTest=
+