glz::patch support for all glz::generic_ types

[stephenberry]

Add generic_i64 and generic_u64 support to JSON patch functionality

Closes #2385

Summary

The JSON patch module (patch.hpp) was hardcoded to use glz::generic (f64 mode) throughout. This meant that glz::generic_i64 and glz::generic_u64 could not be used with any patch operations, losing integer precision for values beyond what double can represent.

This PR templatizes the entire JSON patch module so that all operations (RFC 6902 patch, RFC 7386 merge patch, and diff) work with any generic_json specialization.

Changes

include/glaze/json/patch.hpp

• Added is_generic_json type trait and concept to detect any generic_json<Mode, MapType> specialization
• Templatized patch_op and patch_document into patch_op_t<GenericType> and patch_document_t<GenericType>, with backward-compatible aliases (patch_op = patch_op_t<>, patch_document = patch_document_t<>)
• Templatized all helper functions (equal, navigate_to_parent, insert_at, remove_at), operation functions (apply_add/remove/replace/move/copy/test), diff, patch, and merge patch functions
• Fixed the std::visit in diff_impl to use typename GenericType::object_t/array_t instead of hardcoded generic:: types, with a generic else branch that handles all scalar types (double, int64_t, uint64_t, string, bool)
• Updated the not_generic concept to exclude all generic_json specializations (previously only excluded generic)

tests/json_test/json_patch_test.cpp

• Added generic_i64_patch_tests suite (9 tests): add, replace with precision preservation, diff/patch round-trip, test, move, merge patch, merge diff, patched (non-mutating), patch_json string convenience
• Added generic_u64_patch_tests suite (5 tests): add, diff/patch round-trip, test, merge patch, patch_json string convenience

Backward Compatibility

All changes are fully backward compatible. Existing code using patch_op, patch_document, diff(), patch(), merge_patch(), etc. continues to work without modification. All 64 original tests pass unchanged alongside the 14 new tests (78 total, 300 assertions).