perf(test): activate schema-dump fast path (WS-6)

mysql-client is now installed on the dev host (brew install
mysql-client + PATH=/opt/homebrew/opt/mysql-client/bin), which
unblocks the fast path that session 2.7 prepared but couldn't
activate.

Changes:
- api/database/schema/mysql-schema.sql committed (current state, 122 KB,
  1749 lines, all 155 migration records).
- api/database/schema/.gitignore removed: the dump is no longer opt-in,
  it's the default code path (active in dev + CI).
- Makefile schema-dump target simplified: drops the docker exec mysqldump
  workaround in favour of plain `php artisan schema:dump`. Now also runs
  migrate to head first so the dump always reflects the latest migration
  set without manual prep.
- CLAUDE.md "Schema dumps" rewritten: "opt-in fast path" → "CI fast
  path", reflects that the dump is committed by default and contributors
  regenerate via `make schema-dump` after adding migrations.

Backfill test wall-time, 4 classes combined:
- Session 2.7 baseline: 127.90s
- This session:          27.55s (78% reduction)

Per class (PHPUnit Duration):
- FormFieldBindingMigrationTest:        4.59s  (2 tests)
- ConditionalLogicBackfillTest:         5.45s  (4 tests)
- FormFieldOptionsBackfillTest:        12.25s  (9 tests)
- FormFieldValidationRuleBackfillTest: 10.75s  (6 tests)

Full suite knock-on: 209.95s → 89.16s (-57%) — every RefreshDatabase
test pays the up-front migrate cost, which `schema:dump` collapses
from ~6s × N to a single ~1s SQL load.

Refs: WS-6 session 2.7 deviation #3 cleanup, Q1 closure

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

api/database/schema/.gitignore

@@ -1,4 +0,0 @@
-# Schema dumps are environment-specific and require mysql CLI on host
-# for Laravel's auto-load. NOT committed by default. See CLAUDE.md
-# "Schema dumps (opt-in fast path)".
-mysql-schema.sql