WW-5653 Upgrade Bootstrap to 5.3.x in sample apps

[lukaszlenart]

Fixes WW-5653

Migrates both sample apps — apps/showcase and apps/rest-showcase — off the vendored Bootstrap 3.3.4 assets onto Bootstrap 5.3.7, served via the framework's own <s:webjar> support. This is a minimal port: pages keep their structure and look; only what Bootstrap 5 breaks was changed. Zero vendored Bootstrap 3 assets and zero Bootstrap 3 markup remain.

Design + plan: docs/superpowers/specs/2026-07-17-WW-5653-bootstrap5-migration-design.md, docs/superpowers/plans/2026-07-17-WW-5653-bootstrap5-migration.md.

What changed

Asset delivery (WebJars)

• Added org.webjars:bootstrap:5.3.7 and org.webjars.npm:bootstrap-icons:1.13.1 (managed in parent/pom.xml, version props in root pom.xml); both apps depend on them.
• Deleted all vendored Bootstrap/jQuery static files; references now use <s:webjar> (bootstrap/css/bootstrap.min.css, bootstrap/js/bootstrap.bundle.min.js, bootstrap-icons/font/bootstrap-icons.min.css, jquery/jquery.min.js).
• WebJar allowlist configured per app (struts.webjars.allowlist).

jQuery isolation (note for reviewers)

• The showcase keeps jQuery (2 direct usages: prettyPrint + an AJAX demo), pinned to 3.7.1 via a dedicated webjars-jquery-showcase.version property. The shared webjars-jquery.version (now 4.0.0, core test scope) is intentionally not reused, so a future bump of the shared property won't drag the showcase to jQuery 4. Bootstrap 5 itself needs no jQuery.

Markup migration (BS3/BS2 → BS5)

• Icons: glyphicon-* (and old BS2 icon-*) → Bootstrap Icons bi bi-*.
• panel*→card*, btn-default→btn-secondary, btn-large→btn-lg, well→bg-light border rounded p-3, pull-*→float-*/ms-auto, table-condensed→table-sm, col-xs-*→col-*, BS2 spanN→col-N, col-sm-offset-2→offset-sm-2, data-*→data-bs-*, page-header/hero-unit replaced, carets removed.
• Navbar rewritten to BS5 (navbar-expand-lg, toggler + collapse, dropdown-toggle/dropdown-menu/dropdown-item).
• rest-showcase horizontal forms → BS5 (row mb-3 + col-form-label); fixed a pre-existing malformed </apan> tag.

Runtime verification (manual, both apps under mvn jetty:run)

• showcase: home + fileupload + wait + tag-demo pages return 200; all webjar assets serve 200 (Bootstrap CSS/JS bundle, Bootstrap Icons CSS, jQuery 3.7.1); remaining webapp assets (prettify.js, main.css) still serve.
• rest-showcase: order pages render; Bootstrap + Bootstrap Icons CSS serve 200; bi icons render; no glyphicons in output.
• Core webjar tests: 18/18 pass (jQuery 4.0.0 test-scope unaffected).

Dogfooding find (already fixed here)

Serving the showcase via <s:webjar> surfaced a real bug in the showcase's own config: struts.action.excludePattern still whitelisted the old vendored layout (.*/styles/.*\.css, .*/js/.*\.js). The .*/js/.*\.js entry matched the webjar JS path (/static/webjars/bootstrap/5.3.7/js/bootstrap.bundle.min.js), so StrutsExecuteFilter excluded it from the static handler and it fell through to the container and 404'd (silently — no Struts logs). The CSS worked only because its webjar path is under /css/, not /styles/. Fixed by dropping the obsolete /styles/ and /js/ exclude entries. No core/framework code was changed — this is showcase config only.

Draft — remaining follow-up nits (non-blocking)

• Leftover harmless BS3 navbar-header wrapper div in decorators/main.jsp (no BS5 CSS behind it).
• page-header replacement is border-bottom pb-2 mb-3 on most pages vs a bare <div> on a few — both valid, slightly inconsistent.
• navbar-light is soft-deprecated in BS 5.3 (works fine in 5.3.7; data-bs-theme is the newer idiom).
• Pre-existing orphan dropdown-submenu/unclosed <li> in the navbar Examples menu (not introduced here).

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