feat: add memind server module

[starboyate]

Summary

• add the memind-server Spring Boot module with admin APIs, open APIs, runtime configuration management, rerank wiring, sample config, and schema initialization support
• add MyBatis Plus based admin query/delete flows, runtime config persistence, and end-to-end tests for server controllers, services, schema bootstrap, and runtime behavior
• refactor conversation buffer persistence in JDBC and MyBatis Plus plugins so pending and recent views share one persisted conversation log table
• harden full-context memind-server tests by isolating Spring AI OpenAI auto-configuration and providing noop runtime beans so the suite does not depend on real API keys

Test Plan

• mvn -pl memind-server -am -Dtest=MemindServerApplicationTest,MemindServerSqliteBootstrapTest,MemindServerIntegrationTest -Dsurefire.failIfNoSpecifiedTests=false test
• mvn -pl memind-server,memind-plugins/memind-plugin-jdbc,memind-plugins/memind-plugin-spring-boot-starters/memind-plugin-jdbc-starter,memind-plugins/memind-plugin-spring-boot-starters/memind-plugin-mybatis-plus-starter,memind-plugins/memind-plugin-spring-boot-starters/memind-plugin-ai-spring-ai-starter -am test -Dsurefire.failIfNoSpecifiedTests=false

Notes

• memind-server/src/main/resources/application.yml no longer carries committed API keys or provider secrets.
• The Maven runs emit a non-fatal JaCoCo instrumentation warning for net.sf.jsqlparser.parser.CCJSqlParserTokenManager; tests and build still pass.