feat(10-02): implement requireAdmin DB-backed MiddlewareHandler

- reads users.isAdmin from DB (never trusts context user's isAdmin claim)
- 403 with { error: 'Forbidden' } for non-admins and missing user
- side-effect import of devBypass.js for ContextVariableMap augmentation
- bypass path skips OIDC only, not the DB check (T-10-04/T-10-05)

apps/api/src/lib/requireAdmin.ts

@@ -0,0 +1,47 @@
+/**
+ * requireAdmin — MiddlewareHandler that DB-enforces the admin role (ADMIN-03).
+ *
+ * Security contract (T-10-04, T-10-05):
+ *   - Reads users.is_admin from the DB — the bypass only skips OIDC, not this check.
+ *   - Never branches on a property of c.get('user') other than .id.
+ *   - Non-admins and unauthenticated requests always receive 403 { error: 'Forbidden' }.
+ *   - Never logs the user object or any credential (T-10-07).
+ *
+ * Mount FIRST inside any admin sub-router:
+ *   adminRouter.use('*', requireAdmin);
+ *
+ * The side-effect import of devBypass.js carries the ContextVariableMap augmentation
+ * so c.get('user') is statically typed (same pattern as other route files).
+ */
+
+// Side-effect import: ContextVariableMap augmentation for c.get('user')
+import '../auth/devBypass.js';
+
+import type { MiddlewareHandler } from 'hono';
+import { eq } from 'drizzle-orm';
+import { db } from '../db/client.js';
+import { users } from '../db/schema.js';
+
+export const requireAdmin: MiddlewareHandler = async (c, next) => {
+  const contextUser = c.get('user') as { id: number } | undefined;
+  const userId = contextUser?.id;
+
+  // No resolved user — 403 immediately, no DB query
+  if (!userId) {
+    return c.json({ error: 'Forbidden' }, 403);
+  }
+
+  // Always look up is_admin from the DB.
+  // The dev-auth bypass skips OIDC, not the DB check — this lookup runs on every request.
+  const [row] = await db
+    .select({ isAdmin: users.isAdmin })
+    .from(users)
+    .where(eq(users.id, userId))
+    .limit(1);
+
+  if (!row?.isAdmin) {
+    return c.json({ error: 'Forbidden' }, 403);
+  }
+
+  await next();
+};