fix(dev-portal): restore stroke=currentColor on sidebar icons (closes #48)

[pascal-klesse]

Summary

• Restores visibility of dev-portal sidebar icons that broke during the shadcn migration in feat(dev-portal): migrate SPA to shadcn/ui + tailwind 4 (closes #40) #41 — every inline <svg> was rendered with fill="none" but no stroke, so the <path> / <line> / <circle> elements painted nothing.
• Adds four Lucide-style stroke attributes to the shared COMMON props in src/core/dx/clients/layout/icons.tsx: stroke="currentColor", strokeWidth={1.75}, strokeLinecap="round", strokeLinejoin="round". The wrapper text-… utilities on AdminShell already supply the colour, including the active-state accent (text-accent).
• Pins the regression in tests/stories/dev-portal-pages.story.test.ts so a future refactor can't silently drop the stroke attributes again.

Why this works

The legacy CSS rule that compensated for the missing stroke (.admin-nav__icon svg path { stroke: currentColor; } in the deleted admin-layout.css) is gone. Adding the stroke attributes directly on the SVG closes the gap and keeps icon colour inheritance flowing through currentColor — exactly what text-accent on the active <NavLink> already drives.

BRAND_LOGO already declared its strokes inline and was unaffected.

Acceptance criteria (Issue #48)

• COMMON props extended with stroke="currentColor" + strokeWidth={1.75} + strokeLinecap="round" + strokeLinejoin="round"
• Story-test in tests/stories/dev-portal-pages.story.test.ts asserts the four stroke attributes are present
• Active-state (lime accent) propagates via currentColor inheritance — no callsite changes needed
• Visual smoke test: sidebar icons render visibly across all sections (human reviewer)

Test plan

• bun run lint — clean
• bun run format — clean
• bun run test:types — clean
• bun run test:unit — 153/153 passed
• bun run test:e2e — 2412/2412 passed (story-test pin transitioned RED → GREEN)
• bun run test:coverage — 91.09% statements / 81.88% branches / 92.96% lines, thresholds met
• bun run build:dev-portal — 57 artifacts (971.7 kB)
• bun run build — full server build clean
• Visual smoke test on bun run dev (human reviewer): every sidebar section icon visible, active-state lime tint correct

Out of scope

• Migration to lucide-react (breaking — icon names + paths change)
• Adding new icons for pages without one

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