Editor: Fix NPE when generating schema from PostgreSQL views

[PZahnen]

Closes ldproxy/editor#29

• SchemaCrawler returns view definitions wrapped as CREATE OR REPLACE VIEW … AS …, which JSQLParser parses as CreateView, not Select. The old code's blind cast to Select triggered a ClassCastException that setErrorRecovery(true) silently turned into a null result.
• The following getSelectBody() call on null threw an NPE that wasn't caught locally and ultimately killed schema generation for the affected view, leaving types: {} in the generated YAML.
• ViewInfo.parse() now handles both Select and CreateView (unwrapping the latter), and rejects anything else via a regular JSQLParserException that existing catch blocks handle gracefully.
• SchemaGeneratorSql now logs a WARN for failed per-table generation and filters out null results, so a single problematic table can no longer break the whole run.