Report the JDBC URL from DatabaseMetaData.getURL() instead of the transport endpoint #274

Problem

LibsqlDatabaseMetaData.getURL() returns connection.getConfig().url(), which is the
transport endpoint, not the JDBC URL the caller used. DatabaseMetaData.getURL() is
specified to return the URL for the database, so this loses the jdbc: scheme and the
prefix.

Current values:

• jdbc:libsql:http://host:port → getURL() returns http://host:port
• jdbc:sqlite:http://host:port → getURL() returns http://host:port
• WebSocket connections → ws://... or wss://...

WebSocketTransportIT#metadataAndBatchWorkOverWebSocket pins the endpoint value.

Why it matters

URL-based consumers cannot recognize the database. jOOQ 3.21's
JDBCUtils.dialect(Connection) reads DatabaseMetaData.getURL() and matches known JDBC
prefixes. The endpoint has no jdbc:... prefix, so jOOQ returns SQLDialect.DEFAULT
even for a jdbc:sqlite: connection. JooqIT#dialectDetectionUsesTheUrlNotTheProductName
currently pins that fallback.

With the original JDBC URL, jOOQ would select SQLDialect.SQLITE for the
jdbc:sqlite: alias. jdbc:libsql: would still need an explicit dialect because jOOQ
has no libsql prefix; that is acceptable and already documented.

Where

• libsql-jdbc/src/main/java/io/github/magnusp/libsql/jdbc/LibsqlDatabaseMetaData.java:191
• libsql-jdbc/src/main/java/io/github/magnusp/libsql/jdbc/LibsqlDriver.java:34 knows
  the original URL and can pass it to LibsqlConnection.
• libsql-itests/src/test/java/io/github/magnusp/libsql/itest/WebSocketTransportIT.java:111
  pins the current endpoint value.

Fix

Preserve the URL passed to LibsqlDriver.connect on LibsqlConnection and return it
from LibsqlDatabaseMetaData.getURL(). Keep config.url() for the transport.

Verification

• Unit test getURL() for jdbc:libsql: and jdbc:sqlite: over HTTP.
• Update WebSocketTransportIT to expect the jdbc:libsql: URL.
• JooqIT: alias connection → SQLDialect.SQLITE; jdbc:libsql: → SQLDialect.DEFAULT.
• ./mvnw -pl libsql-jdbc -am verify and ./mvnw spotless:check.

Found while correcting the jOOQ dialect pin in #261/#268.