feat: minimal signals + RemoteData template with a users feature

Extracted from atomic-design-poc: RemoteData<E,T> (bare union + fromResource,
no combinators) + a trimmed <app-async> switch, no Elm-style store — state is
resource() plus one plain signal. Minimal DDD layering per context
(domain/infrastructure/application/ui) combined with atomic design inside
ui/ (atoms/molecules/organisms/templates/pages), mirroring the POC's
conventions at template scale.

One worked feature (users/): a list with a click-through to a detail view
(its own independent resource() fetch) and a Back action. Tests are
BDD-style (describe/it, one assertion per it) and black-box (assert
rendered DOM/emitted events only) - 100% branch/line coverage. README.md
documents what's deliberately omitted vs. the POC and the concrete growth
path back to it.

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

package.json

@@ -24,9 +24,10 @@
     "@angular/build": "^22.1.2",
     "@angular/cli": "^22.1.2",
     "@angular/compiler-cli": "^22.1.0",
+    "@vitest/coverage-v8": "^4.1.10",
     "jsdom": "^28.0.0",
     "prettier": "^3.8.1",
     "typescript": "~6.0.2",
     "vitest": "^4.0.8"
   }
-}
+}