feat: add Docker Compose support for Discord bot deployment

- Add Dockerfile with multi-stage build for picoclaw
- Add docker-compose.discord.yml for Discord bot service
- Add docker-compose.yml for agent mode service
- Add .env.example with environment variable template
- Add .dockerignore for optimized builds
- Update README.md with Docker Compose section and language switch
- Add README.ja.md (Japanese documentation)
- Update .gitignore with Docker-related entries

.env.example

@@ -0,0 +1,17 @@
+# ── LLM Provider ──────────────────────────
+# Uncomment and set the API key for your provider
+# OPENROUTER_API_KEY=sk-or-v1-xxx
+# ZHIPU_API_KEY=xxx
+# ANTHROPIC_API_KEY=sk-ant-xxx
+# OPENAI_API_KEY=sk-xxx
+# GEMINI_API_KEY=xxx
+
+# ── Chat Channel ──────────────────────────
+# TELEGRAM_BOT_TOKEN=123456:ABC...
+# DISCORD_BOT_TOKEN=xxx
+
+# ── Web Search (optional) ────────────────
+# BRAVE_SEARCH_API_KEY=BSA...
+
+# ── Timezone ──────────────────────────────
+TZ=Asia/Tokyo