feat(nexa_coa_setup): pre_init_hook to clear l10n_ca code collisions

Bakes the staging-side one-off collision clearing into the module install
itself so production install will execute the same sweep automatically.

For each of the 29 l10n_ca codes that conflict with Nexa's planned chart:
- If the account has zero postings: suffix code with '.OLD', mark inactive,
  rename to '(l10n_ca LEGACY) <original>'
- If the account has postings (currently 115100 AR control with 240 lines
  and 511100 Inside Purchases with 1 line): leave alone (Nexa renumbered
  to 119100 / 511105 in the XML)

Idempotent — pre_init_hook re-running has no effect (already-suffixed
codes are skipped).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

nexa_coa_setup/__init__.py

@@ -1,2 +1,2 @@
 from . import models
-from .hooks import post_init_hook
+from .hooks import pre_init_hook, post_init_hook