T-1: initialize monorepo structure with backend and frontend scaffolds

Backend: Spring Boot 3.5.11 on Java 25, Maven with wrapper, hexagonal
architecture package layout (domain/application/adapter/config), health
endpoint with integration test. Originally planned for Spring Boot 4.0
but pivoted due to massive package reorganization in 4.0 (see addenda
in research and plan docs).

Frontend: Vue 3 scaffolded via create-vue with TypeScript, Vue Router,
Vitest, ESLint, Prettier. Pivoted from Svelte due to ecosystem maturity
concerns (broken router ecosystem for Svelte 5).

Also: extended .gitignore for Java/Maven and Node/Vue artifacts, updated
CLAUDE.md with tech stack, build commands, agent documentation sections,
and document integrity rule.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/assets/main.css

@@ -0,0 +1,35 @@
+@import './base.css';
+
+#app {
+  max-width: 1280px;
+  margin: 0 auto;
+  padding: 2rem;
+  font-weight: normal;
+}
+
+a,
+.green {
+  text-decoration: none;
+  color: hsla(160, 100%, 37%, 1);
+  transition: 0.4s;
+  padding: 3px;
+}
+
+@media (hover: hover) {
+  a:hover {
+    background-color: hsla(160, 100%, 37%, 0.2);
+  }
+}
+
+@media (min-width: 1024px) {
+  body {
+    display: flex;
+    place-items: center;
+  }
+
+  #app {
+    display: grid;
+    grid-template-columns: 1fr 1fr;
+    padding: 0 2rem;
+  }
+}