Builds locations, items, per-location stock, and a stock-movement audit
ledger (receive/withdraw/adjust) on top of the existing hand-rolled MVC
framework, gated behind the existing user login. Low-stock withdrawals/
adjustments queue an email alert. Adds a custom "positive_integer"
validation rule and a generic SMTP email driver (alongside the existing
Postmark one) to demonstrate the framework's documented extension points.

Removes the Product/Order rocket-shop demo and renumbers the surviving
migrations (users/profiles/jobs) since nothing had been deployed from the
single "Initial commit" yet.

Also fixes local dev environment issues hit while building this: Windows
reserves the original 8081/8081 Docker port mapping and 9090 in its dynamic
TCP exclusion range (now 9092/9091, documented in the readme), and
docker/start-container.sh had CRLF line endings from a Windows checkout that
broke its shebang inside the container (.gitattributes now forces *.sh to
LF).

Adds AGENTS.md/CLAUDE.md documenting environment gotchas and two real
framework bugs found along the way (Route::matches() not checking HTTP
method for parameterised paths, and required validation rejecting "0" due
to PHP's empty("0") === true) so they aren't re-discovered from scratch.

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