fix(jdbc): fold transaction modes and table types with Locale.ROOT #286

What happens

TransactionMode.from and MetadataSql call toUpperCase() without a locale. Under a Turkish default locale, "immediate" folds to "İMMEDİATE", so TransactionMode.from("immediate") throws IllegalArgumentException. MetadataSql folds TABLE_TYPE values the same way, so getTables(..., new String[] {"VIEW"}) builds a predicate that matches nothing.

The probe ran against the built classes during the independent verification of #285. The full result is in #285 (comment).

Sites

• LibsqlConnection.java:99 uses mode.toUpperCase().
• MetadataSql.java:36 uses types[i].toUpperCase().

Fix

Use Locale.ROOT at both sites. This is the same policy as the rest of the driver after #283.

Pins

• A test that sets Locale.setDefault(Locale.forLanguageTag("tr")) and asserts TransactionMode.from("immediate") returns IMMEDIATE and from("exclusive") returns EXCLUSIVE.
• A test that builds the getTables predicate under the same default and asserts the VIEW type literal is VIEW.
• Add restrict or no action to the ForeignKeyMetadata locale pin in LocaleFoldingTest, so the FK call site is mutation-sensitive too. The current cascade and set null cases contain no Turkish-sensitive letter.

Acceptance

• Both sites use Locale.ROOT.
• The new tests fail under the Turkish default before the fix and pass after it.
• ./mvnw -pl libsql-jdbc -am test is green.
• ./mvnw spotless:check is green.
• Public API, exception types, and messages are unchanged.

Refs #283, #282.