Feature/named parameter support

[bgunebakan]

Summary of the changes / Why this is an improvement

Adds client-side named parameter support (pyformat paramstyle) to the CrateDB Python client, addressing the request in #774.

Previously, cursor.execute() only accepted positional ? placeholders. Users with complex SQL had to maintain a positional list that was error-prone and hard to read.

With this change, a dict can be passed as the parameters argument using %(name)s placeholders:

cursor.execute(
    "SELECT * FROM t WHERE city = %(city)s AND kiez = %(kiez)s",
    {"city": "Berlin", "kiez": "Kreuzberg"},
)

The same parameter name may appear multiple times in the query, each occurrence is resolved independently:

cursor.execute(
    "SELECT * FROM t WHERE state = %(q)s OR city = %(q)s",
    {"q": "Berlin"},
)

Positional ? queries continue to work unchanged, no breaking change.

Known limitation

Supporting named params in bulk operations are not supported because it requires a different approach from execute(). We need to extract the ordered parameter name list from the SQL. Excluded from this PR to keep this PR focused on the core execute() case.

Checklist

• Link to issue this PR refers to (if applicable): Fixes Parameter binding failure with string containing "{{value}}" and lack of named parameter support #774