📝 docs: add ADR-0023 for config hot reloading strategy

Adds Architecture Decision Record 0023 proposing selective hot reloading
for configuration changes. The ADR analyzes different approaches and
recommends implementing hot reloading only for safe parameters like
logging level, feature flags, and telemetry settings while requiring
restart for critical parameters like server settings and credentials.

The ADR includes:
- Problem statement and decision drivers
- Analysis of 4 different approaches
- Detailed implementation strategy
- Safety considerations and error handling
- Migration plan and future enhancements

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

adr/README.md

@@ -81,6 +81,7 @@ Chosen option: "[Option 1]" because [justification]
 * [0020-docker-build-strategy.md](0020-docker-build-strategy.md) - Docker Build Strategy: Traditional vs Buildx
 * [0021-jwt-secret-retention-policy.md](0021-jwt-secret-retention-policy.md) - JWT Secret Retention Policy with Configurable TTL and Retention
 * [0022-rate-limiting-cache-strategy.md](0022-rate-limiting-cache-strategy.md) - Rate Limiting and Cache Strategy with Multi-Phase Implementation
+* [0023-config-hot-reloading.md](0023-config-hot-reloading.md) - Config Hot Reloading Strategy
 
 ## How to Add a New ADR