feat: implement OmegaConf-based configuration management with uv

Configuration changes:
- Replace pydantic-settings with OmegaConf for flexible config management
- Support YAML config files via CONFIG_FILE environment variable
- Support environment variables with STEWARD__SECTION__KEY format
- Add config_schema.yaml as default configuration schema
- Create pydantic models for each configuration section for type safety
- Maintain backward compatibility via properties on Settings class
- Add CONFIGURATION.md with comprehensive setup and usage guide
- Update pyproject.toml to include config_schema.yaml in package data

Build/deployment changes:
- Replace pip with uv in Dockerfile for faster dependency installation
- Create docker-compose.dev.yml for local development (build .)
- Keep docker-compose.yml for production (uses ghcr.io/djw4/steward:latest)
- Update .env.example with new STEWARD__* variable format

This setup is designed for Kubernetes deployment:
- Non-sensitive config goes in ConfigMap (config.yaml)
- Secrets go in Secret resources (environment variables)
- Single unified configuration system for all environments

config.example.yaml

@@ -0,0 +1,69 @@
+# Example Steward Configuration (config.yaml)
+#
+# This file demonstrates how to configure Steward using a YAML config file.
+#
+# To use this config:
+#   1. Copy this file to your deployment location (e.g., /etc/steward/config.yaml)
+#   2. Set the CONFIG_FILE environment variable: CONFIG_FILE=/etc/steward/config.yaml
+#   3. Secrets should still be provided via environment variables (see below)
+#
+# Configuration Precedence:
+#   1. Environment variables (STEWARD__SECTION__KEY=value) - HIGHEST
+#   2. CONFIG_FILE YAML file
+#   3. Default values - LOWEST
+#
+# Secret Management:
+#   - Never put secrets (API keys, tokens) in this YAML file
+#   - Use environment variables instead:
+#     * STEWARD__TELEGRAM__BOT_TOKEN
+#     * STEWARD__OPENAI__API_KEY
+#     * STEWARD__ANALYSIS__TARGET_API_KEY
+#     * STEWARD__TOOLS__MCP_SERVER_API_KEY
+
+telegram:
+  # Bot token is REQUIRED and should be set via STEWARD__TELEGRAM__BOT_TOKEN env var
+  bot_token: ""
+
+  # List of user IDs allowed to interact via DM (empty = all users allowed)
+  allowed_user_ids:
+    - 1234567890
+    - 9876543210
+
+  # List of group/channel IDs where bot operates (empty = all groups allowed)
+  group_ids:
+    - -1005308306472
+
+openai:
+  # API key should be set via STEWARD__OPENAI__API_KEY env var
+  api_key: ""
+
+  # Base URL for OpenAI-compatible API
+  base_url: "https://api.openai.com/v1"
+
+  # Model to use
+  model: "gpt-4o"
+
+  # Custom system prompt (optional)
+  system_prompt: "You are Steward, a persistent, trustworthy AI-assisted personal operations platform. You reduce cognitive load by observing, remembering, planning, and proposing actions. You are conservative, transparent, and policy-aware. Always explain your reasoning."
+
+analysis:
+  # Optional: URL for API analysis/proposals
+  target_url: ""
+
+  # Optional: API key for analysis target (set via STEWARD__ANALYSIS__TARGET_API_KEY)
+  target_api_key: ""
+
+  # Schedule for automatic analysis (cron-like)
+  cron_hour: 8
+  cron_minute: 0
+
+memory:
+  # Path to persistent thread memory storage
+  thread_memory_path: "/data/thread_memory.json"
+
+tools:
+  # Optional: MCP/OpenAPI tool server URL
+  mcp_server_url: ""
+
+  # Optional: API key for MCP server (set via STEWARD__TOOLS__MCP_SERVER_API_KEY)
+  mcp_server_api_key: ""