Week 4 (scoped): BooksRun live price/stock check + daily FTP sync stub

Adds a live per-ISBN BooksRun API check to the checkout-time price
recheck (Order\PriceRecheck) so a booksrun-sourced offer is verified
fresh, not trusted from a potentially day-stale local cache -- fails
closed on any problem (API error, no stock), matching Appendix B's
"stale supplier cost must never be trusted as final." Live values are
written back to the same offer_id row so SupplierOrderJob's later
fulfillment-time read sees them too.

Also wires a real daily Action Scheduler job (scheduling/dedup/batch-write
infrastructure) for BooksRun's FTP inventory feed, but leaves the actual
connect+parse step (Import\BooksRunOfferSync::connect_and_parse_feed())
as a deliberate stub -- no FTP access or sample feed exists yet, and
guessing at a file format would silently write wrong data once real
access arrives. The stub fails loud on the manual CLI trigger, quiet on
the scheduled job (no point alarming on an expected, known state).

Ingram, BooksRun AutoBuy, production email, and tax/legal/monitoring are
explicitly out of scope for this pass -- narrowed by user request.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01D2gmgaDVXcRGCwLfdXQajD

.env.example

@@ -41,6 +41,13 @@ BACKUP_RETENTION_DAYS=14
 # staging: gutenberg_test   production: booksrun,ingram
 ACTIVE_SUPPLIER_ADAPTERS=gutenberg_test
 BOOKSRUN_API_KEY=
+# Week 4: bulk FTP inventory feed — placeholders, not yet consumed by any
+# code beyond Import\BooksRunOfferSync::is_ftp_configured()'s empty check.
+BOOKSRUN_FTP_HOST=
+BOOKSRUN_FTP_PORT=
+BOOKSRUN_FTP_USER=
+BOOKSRUN_FTP_PASSWORD=
+BOOKSRUN_FTP_REMOTE_PATH=
 INGRAM_API_KEY=
 INGRAM_ACCOUNT_ID=