feat(policies): capture the full premium breakdown

The capture form only ever had prima neta, derecho de póliza and comisión.
The Access form it replaces has seven figures, and the four that were missing
are the ones that make a policy paid in installments add up.

Adds recargo, IVA, prima total and forma de pago to the policy header, the
same breakdown per installment, and a per-line-of-business IVA rate.

IVA and prima total are the only derived figures:

    base  = prima neta + recargo + derecho de póliza
    IVA   = round(base * tasa)
    total = base + IVA

The recargo is inside the taxable base. That is not a guess — policy 7006785
prints IVA 52.03 on 610.86 + 8.55 + 31.00, and leaving the recargo out gives
51.35, which matches nothing on the page. Both of its money rows are asserted
in premium.spec.ts. The recargo itself is never derived: the carrier quotes it,
so staff key it in, and the field is disabled on ANNUAL/SINGLE. Both derived
figures are stored rather than recomputed on read, and stay editable, because
the printed policy is the record of truth and a later rate change must not
silently restate what was issued.

The rate lives on PolicyType (seeded to 0.08, editable in Catálogos), which is
the legacy one-row IMPUESTOS / IMPUESTOS_AUTOS tables made configurable. The
rate applied is stamped on the policy so an old one reads back at its original
rate.

Per-installment, not two fixed slots on the header: a policy split into several
exhibiciones prices each payment separately — that is why the Access form drew
the money row twice — and a trimestral policy needs four, which the Access
layout could not hold.

Also fixes two losses in the ETL, which is how these went missing:

  - `forma_pago` was marked consumed by the coverage sweep and then never
    written to any column, so FORMA PAGO existed nowhere in the platform.
  - `recargo` and the whole second money row fell into `coveragesJson` as
    loose strings, mislabeled as coverage amounts.

transform_policies.py now writes all of it directly;
backfill_policy_premium_breakdown.py recovers it on a database that must not be
re-imported, and strips the migrated keys back out of coveragesJson. Both are
COALESCE-only, so a figure a human has corrected in the app wins.

IVA and TOTAL are NOT backfilled: they were unbound calculated controls on the
Access form, never columns, so there is nothing to recover and every migrated
policy reads null until it is edited.

The backfill warns on 5 annual policies that carry a non-zero recargo — a
contradiction that predates this change and is left for a human, not silently
corrected.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

packages/database/prisma/migrations/20260818120000_policy_premium_breakdown/migration.sql

@@ -0,0 +1,37 @@
+-- Premium breakdown the Access capture form had and this schema did not:
+-- RECARGO, IVA and PRIMA TOTAL on the policy header, the same six figures per
+-- payment on the installments, and the FORMA PAGO that decides whether a
+-- surcharge applies at all.
+--
+-- IVA and TOTAL were never columns in Access — they were unbound calculated
+-- controls on the form — so there is nothing to backfill for them here and
+-- every migrated row stays null until somebody edits the policy. RECARGO and
+-- the per-installment figures DO exist in the legacy data; they are currently
+-- stranded inside `policies.coveragesJson` (the migration swept every column
+-- it did not model into that blob) and are recovered by
+-- `migration/backfill_policy_premium_breakdown.py`, not by this migration.
+
+ALTER TABLE `policy_types`
+  ADD COLUMN `taxRate` DECIMAL(6, 4) NULL;
+
+ALTER TABLE `policies`
+  ADD COLUMN `surcharge` DECIMAL(12, 2) NULL,
+  ADD COLUMN `tax` DECIMAL(12, 2) NULL,
+  ADD COLUMN `taxRate` DECIMAL(6, 4) NULL,
+  ADD COLUMN `paymentFrequency` ENUM('ANNUAL', 'SEMIANNUAL', 'QUARTERLY', 'MONTHLY', 'SINGLE') NULL;
+
+ALTER TABLE `policy_payment_installments`
+  ADD COLUMN `netPremium` DECIMAL(12, 2) NULL,
+  ADD COLUMN `surcharge` DECIMAL(12, 2) NULL,
+  ADD COLUMN `policyFee` DECIMAL(12, 2) NULL,
+  ADD COLUMN `tax` DECIMAL(12, 2) NULL,
+  ADD COLUMN `taxRate` DECIMAL(6, 4) NULL,
+  ADD COLUMN `total` DECIMAL(12, 2) NULL,
+  ADD COLUMN `commission` DECIMAL(12, 2) NULL;
+
+-- Seed the rate the books actually use. The legacy IMPUESTOS and
+-- IMPUESTOS_AUTOS tables each held exactly one row, both 0.0800, covering the
+-- home and auto lines respectively; applying it to every existing type
+-- reproduces current behaviour rather than changing it. Types created later
+-- start null and fall back to the API default.
+UPDATE `policy_types` SET `taxRate` = 0.0800 WHERE `taxRate` IS NULL;