Config Management: Centralize configuration with validation

[OneByJorah]

Config Management Gap

Current State: Config scattered across config.py, app.py, .env.sample, docker-compose.yml, and processor.py. No validation, no schema, no environment-specific configs.

Required:

1. Centralized config with Pydantic Settings (pydantic-settings)
2. Environment-specific configs (dev, staging, prod)
3. Config validation with clear error messages
4. Remove hardcoded defaults from code
5. Add config schema documentation
6. Support for secrets from vault/secret managers
7. Hot-reload config changes (SIGHUP)
8. Config versioning/migration

Priority: HIGH