feat: support named :name query placeholders

[omer-cengel]

Summary

Queries can now write :name placeholders instead of $N, so parameters read as their meaning and the generated method parameters carry the names the query author chose. Each named placeholder compiles to a JDBC ? and is analyzed wherever an indexed placeholder is.

Changes

• Compile :name (a colon directly followed by an unquoted ASCII identifier, compared exactly as written) to ?; placeholder text in string literals, quoted identifiers, and comments is untouched, and : name is not a placeholder.
• Treat each distinct name as one parameter numbered by its first textual occurrence; every occurrence binds at its own ? position in textual order.
• Accept named placeholders in comparisons with a column on either side, IN lists, LIKE/ILIKE patterns, BETWEEN bounds, INSERT values, UPDATE assignments, LIMIT, and OFFSET; the method parameter is named after the placeholder, so LIMIT :pageSize generates pageSize.
• Reject a query mixing $N and :name, a qualified (:a.b), quoted (:"x"), or &name placeholder anywhere in the statement, a named placeholder in an unanalyzed location, and one name used with conflicting types, with diagnostics that write the placeholder as the query spells it.
• Document the named form, its ordering, and its rejections in the query reference.
• Add parser, compiler, and analyzer tests, a generated-repository compilation and execution test, and a PostgreSQL execution test of a query that repeats a name.

Scope and non-goals

• Queries written only with $N placeholders produce unchanged models, executable SQL, generated code, and diagnostics.
• Cast-typed placeholders such as :name::text, non-placeholder INSERT/UPDATE expressions, = ANY, upsert, @name or macro syntax, and :1 are not supported by this change.
• Code generation, the runtime, configuration, and the sample are unchanged.