Fix Critical Database Performance and Hibernate Issues

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Summary

This PR addresses the critical database performance bottlenecks and Hibernate stack overflow errors identified in the root cause analysis.

Issues Fixed

🔥 Critical Issues

• Database Performance: Added connection pooling and timeout optimizations to PostgreSQL configuration
• Hibernate StackOverflowError: Fixed deleteAllInBatch method causing 2.44% fault rate with native SQL query
• HTTP Client Timeouts: Increased timeout values to prevent 4,000+ ResourceAccessException errors

📊 Performance Improvements

• Connection Pooling: Added CONN_MAX_AGE, MAX_CONNS, MIN_CONNS settings
• Database Timeouts: Set connect_timeout to 10 seconds with proper transaction isolation
• HTTP Timeouts: Increased connection timeout to 30s and read timeout to 60s
• Logging: Enhanced database query logging for monitoring slow queries

Files Changed

• pet_clinic_insurance_service/pet_clinic_insurance_service/settings.py - Database connection pooling
• spring-petclinic-customers-service/src/main/resources/application.yml - HTTP client timeouts
• spring-petclinic-customers-service/.../OwnerRepository.java - Hibernate fix with native query

Expected Impact

• Reduce database query latency from 47+ seconds to sub-second response times
• Eliminate StackOverflowError causing 2.44% fault rate in customers service
• Prevent timeout cascades between customers and insurance services
• Improve overall system availability and reduce error rates

Testing

• Database connection pooling tested with PostgreSQL backend
• HTTP timeout configuration validated for service-to-service calls
• Native SQL query tested to avoid Hibernate HQL parsing issues

Fixes the critical availability issues identified in the Application Signals investigation.