Split 2 god-functions, fix remaining Phase 4 items (3/4 done)

Phase 3 (partial):
- extract_defs.c: split extract_var_names (509 lines) into 4 helpers by
  language group: extract_vars_mainstream, extract_vars_dynamic,
  extract_vars_jvm, extract_vars_config. Dispatcher is ~40 lines.
- pass_httplinks.c: extract apply_prefix_to_func_routes helper, reducing
  resolve_cross_file_group_prefixes cognitive complexity.

494 -> 2 NOLINTs remaining (cypher.c execute_single + sqlite_writer.c
cbm_write_db — the two largest functions in the codebase).

Author: DeusData