Improved the code for better performance and stability.

Performance & Stability Improvements

• Optimized Excel export flows for offers/payments/allocations by using export-specific retrieval, instead of paged Integer.MAX_VALUE queries.
• Refactored filter/sort handling in domain services to reuse shared specification/sort builders and reduce duplicated query logic.
• Improved payment import performance by switching to batch persistence (saveAll) and removing unnecessary per-row optional/save overhead.
• Added DB performance indexes via V1_17__add_performance_indexes.sql for the most-used filter/sort columns (prospect_code, archived, offer_id, embg, status, allocation_strategy).
• Tuned runtime configuration in application.properties:
  • Hibernate batching/fetch tuning
  • Hikari pool sizing/timeouts
  • Thymeleaf cache enabled
  • spring.jpa.open-in-view=false
• Reduced index-unfriendly text filtering by introducing prefix-based filtering (value%) for ID/code-like fields instead of generic %value% matching.
• Added eager fetch (@EntityGraph) for payment list spec query to avoid lazy loading issues after disabling open-in-view.