[morph] Add bank example: models, tests, CLI, Qt 6 GUI, relations + WebAssembly demo

[Yaraslaut]

Summary

A feature-rich example application in examples/bank that demonstrates morph together with the LASTRADA Lightweight ORM (SQLite via ODBC). It exercises morph's headline properties — typed async bridge, sessions/authorization, validation, the subscribe/set<> form flow, local↔remote parity, and the offline queue — against a realistic domain.

The example is opt-in so the default build is unaffected:

cmake -G Ninja -B build -S . -DMORPH_BUILD_BANK_EXAMPLE=ON           # models + tests + CLI
cmake -G Ninja -B build -S . -DMORPH_BUILD_BANK_EXAMPLE=ON -DMORPH_BUILD_BANK_GUI=ON   # + Qt 6 GUI

What's included

10 models — each with wire DTOs + a Lightweight entity + the model + a Catch2 test:

Model	Actions
Auth	register, login, change password, WhoAmI
Account	open/close (checking/savings/credit), list, balance, overdraft, interest
Transaction	deposit, withdraw, atomic transfer, paginated history
Payee	add/remove/list, IBAN validation, set<> streaming
Payment	one-off bill pay, scheduled payments, standing orders
Card	issue, freeze/unfreeze/cancel, daily limit, PIN
Loan	apply, amortization schedule, repay, payoff
Budget	per-category limits, spending-by-kind analytics
Notification	post, list (unread filter), mark read / all read
Statement	date-ranged credit/debit summary across accounts

Cross-cutting

• Tests: 101 assertions / 16 Catch2 cases, all green — including a remote-backend + custom IAuthorizer test and an offline queue + SyncWorker replay test.
• CLI (bank_cli): runs the full scenario on a local then a simulated remote backend with identical call sites.
• Qt 6 GUI (bank_gui): morph::qt::QtExecutor over a local backend; a warm "Claude-inspired" theme; Login, Accounts, Move Money (+ history), Cards, Payees & Bills, and Loans screens. Headless screenshot smoke test via BANK_GUI_SMOKE=<dir> + QT_QPA_PLATFORM=offscreen.

Design notes

• Two type layers: plain-aggregate wire DTOs (Glaze-serialisable) vs Field<>-based Lightweight entities, mapped in the model. Money as integer minor units (no floating point).
• Per-model DataMapper (one connection per strand, lazily opened on the strand thread). Shared ledger_ops for debit/credit/post-entry; transfers/payments/loan disbursements are atomic via SqlTransaction. All persistence uses the typed DataMapper API (no raw SQL).
• BRIDGE_REGISTER_* macros live in the model headers so every .execute() call site sees the ActionTraits specialisation.

Requirements

C++23, unixODBC, and the SQLite3 ODBC driver. The example FetchContent's Lightweight (which pulls reflection-cpp, stdexec, yaml-cpp, libzip), so the first configure is slow. The GUI additionally needs Qt 6 Widgets.

🤖 Generated with Claude Code

[Yaraslaut]

Update — two commits added since this PR was opened

1. Relations refactor (dabb868) — the persistence layer now models the schema with Lightweight relation types instead of raw FK columns:

• BelongsTo<&UserRecord::id> for ownership (user_id) on every owned table; BelongsTo for the id FKs (account_id, nullable counterparty_id, from_account_id, payee_id). Authorization navigates the relation (rec->user->username).
• HasMany inverses: UserRecord::accounts, PayeeRecord::payments; migrations declare real FK constraints.
• Two upstream Lightweight quirks are documented inline and were reported upstream (Non-reflection DataMapper::Update and fluent Query<T>() don't skip HasMany members (compile error / "no such column") Lightweight#517): HasMany resolves the child FK by ordinal member index, and Update/fluent Query<T>() can't handle HasMany-bearing records in the non-reflection build — hence the UserRow/PayeeRow projections.
• Adds tests/test_relations.cpp. Suite is now 17 cases / 131 assertions, green.

2. Self-contained WebAssembly GUI on GitHub Pages (eb2174f) — examples/bank/gui_wasm/ runs the same QML + controllers entirely in the browser, with the morph model layer as the "server in the background" and no external server:

• Lightweight (ODBC) can't run in a browser, so persistence is swapped for an in-memory store (bank/wasm/store.hpp) behind shadow model headers that shine ahead of the native ones on the include path — controllers, DTOs and QML are reused verbatim.
• BankClient is dual-moded (#ifdef __EMSCRIPTEN__): single-threaded LocalBackend over QtExecutor, no thread pool/ODBC. Single-threaded ⇒ no SharedArrayBuffer ⇒ no COOP/COEP ⇒ plain GitHub Pages hosting works.
• The native stack is gated if(NOT EMSCRIPTEN); native build + all 17 tests remain green.
• .github/workflows/wasm-demo.yml builds with a matched host+wasm Qt pair (aqtinstall) and deploys to Pages under /demo/ (coexists with the Doxygen docs).

Hosting note: verified locally that it builds to a valid wasm bundle and serves over plain HTTP. To see it live: this needs to merge to master (the deploy workflow is master-gated) and GitHub Pages must be enabled once for the repo (Settings → Pages → source gh-pages, currently not enabled). Happy to enable Pages via the API and/or trigger a first deploy if you want it live before merge.

🤖 Generated with Claude Code

[Yaraslaut]

🔗 Live demo: https://lastrada-software.github.io/morph/demo/

Open it and you'll land signed in as the seeded demo user (demo / demo1234) with two accounts — open accounts, deposit/withdraw/transfer, issue cards, add payees & pay bills, take a loan. It's the same QML + controllers as the native GUI, with the morph models running in-browser over an in-memory store (no server).

Published manually from the CI-verified build as a preview; once this merges to master, wasm-demo.yml keeps /demo/ updated automatically (the Doxygen docs remain at the site root).