phsl / new-api

Add confirmed multi-select deletion through one batch API request and one
soft-delete statement. Record the affected count and requested IDs in a
separate batch audit event, and identify legacy events with missing counts.

After creation, offer an unchecked Save as a file option with TXT/Markdown
formats and optional name/quota fields. Keep Done as the default completion
action. Include translations for all seven frontend locales.

Validation:
- Redemption and audit frontend regression tests, typecheck, and scoped lint.
- go build ./...
- go test ./controller -run '^TestDeleteRedemptionBatch$' -count=1 -v
  with TEST_MYSQL_DSN, TEST_MYSQL_LOG_DSN, TEST_POSTGRES_DSN,
  and TEST_POSTGRES_LOG_DSN set to isolated primary and log databases.
- Real SQLite 3.50.4, MySQL 8.4.11, and PostgreSQL 16.15 passed, including
  deletion of 15 records, duplicate/missing IDs, zero-row retries, audit
  deduplication, invalid input, and exclusion of credentials from logs.