feat: implement configuration management service with Pydantic Settings (#53)

- Add pydantic-settings dependency
- Create centralized config.py with nested settings groups:
  - DatabaseSettings: PostgreSQL connection validation
  - RedisSettings: Redis connection with defaults
  - PolygonSettings: RPC endpoints with fallback support
  - PolymarketSettings: WebSocket URL and optional API key
  - DiscordSettings: Optional webhook for alerts
  - TelegramSettings: Optional bot token/chat ID for alerts
- Implement singleton pattern with get_settings() and LRU cache
- Add redacted_summary() for logging config without exposing secrets
- Support .env file loading via python-dotenv
- Add comprehensive test suite (26 tests)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

uv.lock

@@ -1547,6 +1547,7 @@ dependencies = [
     { name = "prometheus-client" },
     { name = "py-clob-client" },
     { name = "pydantic" },
+    { name = "pydantic-settings" },
     { name = "python-dotenv" },
     { name = "redis" },
     { name = "scikit-learn" },
@@ -1578,6 +1579,7 @@ requires-dist = [
     { name = "prometheus-client", specifier = ">=0.19.0" },
     { name = "py-clob-client", specifier = ">=0.1.0" },
     { name = "pydantic", specifier = ">=2.0.0" },
+    { name = "pydantic-settings", specifier = ">=2.0.0" },
     { name = "pytest", marker = "extra == 'dev'", specifier = ">=7.0.0" },
     { name = "pytest-asyncio", marker = "extra == 'dev'", specifier = ">=0.21.0" },
     { name = "pytest-cov", marker = "extra == 'dev'", specifier = ">=4.0.0" },
@@ -1903,6 +1905,20 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/36/c7/cfc8e811f061c841d7990b0201912c3556bfeb99cdcb7ed24adc8d6f8704/pydantic_core-2.41.5-pp311-pypy311_pp73-win_amd64.whl", hash = "sha256:56121965f7a4dc965bff783d70b907ddf3d57f6eba29b6d2e5dabfaf07799c51", size = 2145302, upload-time = "2025-11-04T13:43:46.64Z" },
 ]
 
+[[package]]
+name = "pydantic-settings"
+version = "2.12.0"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "pydantic" },
+    { name = "python-dotenv" },
+    { name = "typing-inspection" },
+]
+sdist = { url = "https://files.pythonhosted.org/packages/43/4b/ac7e0aae12027748076d72a8764ff1c9d82ca75a7a52622e67ed3f765c54/pydantic_settings-2.12.0.tar.gz", hash = "sha256:005538ef951e3c2a68e1c08b292b5f2e71490def8589d4221b95dab00dafcfd0", size = 194184, upload-time = "2025-11-10T14:25:47.013Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/c1/60/5d4751ba3f4a40a6891f24eec885f51afd78d208498268c734e256fb13c4/pydantic_settings-2.12.0-py3-none-any.whl", hash = "sha256:fddb9fd99a5b18da837b29710391e945b1e30c135477f484084ee513adb93809", size = 51880, upload-time = "2025-11-10T14:25:45.546Z" },
+]
+
 [[package]]
 name = "pygments"
 version = "2.19.2"