feat(api,web): auth et first-run — bootstrap admin, login, session, gardes

- api: auth controller/service, config env
- web: App/LoginPage/ProfilePage, garde d'auth, client API, styles
- shared: types/contrats auth
- compose: variables d'environnement first-run

Refs: #14

apps/web/src/styles/app.css

@@ -326,6 +326,45 @@ input {
   background: rgba(169, 72, 52, 0.18);
 }
 
+.success-ribbon {
+  margin: 10px 0;
+  padding: 10px 12px;
+  border: 1px solid rgba(45, 111, 99, 0.72);
+  border-radius: var(--radius);
+  color: #d8fff5;
+  background: rgba(45, 111, 99, 0.18);
+}
+
+.initial-admin-box {
+  display: grid;
+  grid-template-columns: auto minmax(0, 1fr);
+  gap: 10px;
+  margin: 12px 0;
+  padding: 12px;
+  border: 1px solid rgba(213, 168, 77, 0.45);
+  border-radius: var(--radius);
+  background: rgba(213, 168, 77, 0.12);
+}
+
+.initial-admin-box div {
+  display: grid;
+  gap: 4px;
+  min-width: 0;
+}
+
+.initial-admin-box code {
+  width: max-content;
+  max-width: 100%;
+  overflow-wrap: anywhere;
+  color: var(--brass);
+}
+
+.muted-copy,
+.initial-admin-box span,
+.initial-admin-box small {
+  color: var(--ink-muted);
+}
+
 .retry-row {
   display: flex;
   align-items: center;