feat: introduce ConnectionProvider for thread-scoped DB manager lifecycle

[lanarimarco]

Goal

Allow any class on the same thread to obtain the same javax.sql.DataSource (and therefore the same java.sql.Connection) within a logical unit of work, without passing the connection explicitly through the call stack.

• reload creates and owns connections — via HikariCP pool (production) or DriverManager (tests)
• Configuration (JDBC URI, credentials, driver, pool sizing) is owned entirely by the caller — reload never reads YAML or external config
• The entry point is ConnectionProvider.withScope(() -> {}) — a thread-scoped scope; no connection name is required at call time
• Inside withScope(), any class retrieves the appropriate manager or DataSource by file name via ConnectionProvider.currentManager(fileName) / requireDataSource(fileName)
• DBFileFactory transparently participates in the active scope — jariko and Java service code share the same Connection on the same thread with no changes to jariko itself
• Outside any scope (jariko standalone, LSP, debug), currentManagerOrNull() returns null and DBFileFactory falls back to its own manager — no behavioural regression

Summary

• Adds ConnectionProvider singleton (base module) with thread-local withScope() lifecycle management for DBMManager instances
• Adds PoolConfig data class for connection pool tuning and poolConfig field on ConnectionConfig
• Moves findConnectionConfigFor + ConnectionConfigComparator from DBFileFactory into the base module (ConnectionConfigResolver.kt)
• DBFileFactory now delegates to ConnectionProvider.currentManagerOrNull() when a scope is active, falling back to its own manager pool — guarantees connection sharing with Java service code on the same thread
• SQL module: adds SQLConnectionPool, SQLPooledDBMManager, ThreadScopedDataSource, ConnectionProviderSqlExtensions, DBMManagerSqlExtensions, and HikariCP dependency

Three-layer design

Layer	Module	Responsibility
General scope management	reload:base	ConnectionProvider — works for any DBMManager
Convenience wiring	reload:manager	Extension that auto-creates managers via reflection
SQL-specific handle	reload:sql	ThreadScopedDataSource + type-discovery extensions + HikariCP pool
(future) JT400-specific	reload:jt400	toAS400Connection(): AS400?
(future) NoSQL-specific	reload:nosql	toMongoDatabase(): MongoDatabase?

Test plan

• ConnectionProviderTest — unit tests for scope lifecycle, manager reuse, and null-safe fallback
• DBFileFactoryConnectionSharingTest — verifies DBFileFactory reuses the scoped manager when withScope() is active
• SQLConnectionPoolTest — pool acquire/release behaviour
• SQLPooledDBMManagerTest — pooled manager integration
• ConnectionProviderSqlExtensionsTest — SQL-specific provider wiring