docs: add 'When to Activate' sections to 14 skill definitions

Add activation triggers to skills that were missing them, helping
Claude Code determine when to load each skill contextually.

skills/jpa-patterns/SKILL.md

@@ -7,6 +7,15 @@ description: JPA/Hibernate patterns for entity design, relationships, query opti
 
 Use for data modeling, repositories, and performance tuning in Spring Boot.
 
+## When to Activate
+
+- Designing JPA entities and table mappings
+- Defining relationships (@OneToMany, @ManyToOne, @ManyToMany)
+- Optimizing queries (N+1 prevention, fetch strategies, projections)
+- Configuring transactions, auditing, or soft deletes
+- Setting up pagination, sorting, or custom repository methods
+- Tuning connection pooling (HikariCP) or second-level caching
+
 ## Entity Design
 
 ```java