This commit overhauls the pagination system to support flexible ordering
beyond the default created_at timestamp:
- Change CursorKey from fixed byte array to structured object with ID and Value
- Add OrderField and OrderDirection types to support different sorting options
- Update SQLFragment to dynamically generate SQL based on field and direction
- Modify cursor navigation logic to consider custom ordering
- Simplify Position type to use string constants instead of numeric values
- Update Page struct to include reference to Cursor
These changes allow paginated queries to be ordered by different fields
(created_at, updated_at, name) in either ascending or descending order
while maintaining consistent cursor-based pagination behavior.
Signed-off-by: gearnode <bryan@frimin.fr>
