Flatten the repo: move everything out of app/ to the root

Now that the CLI and the Next.js app are one package, nesting it inside
app/ served no purpose - the repo root itself becomes the published
npm package. Merges app/.gitignore and app/README.md into the root
versions, drops the now-duplicate app/LICENSE, and updates path
references (README, docs/ARCHITECTURE.md, docs/CONFIG_REFERENCE.md,
package.json's repository.directory) that assumed the app/ nesting.

Also fixes a real bug this surfaced: the in-app docs viewer resolved
docs/ relative to process.cwd(), which only worked by accident when the
CLI happened to be invoked from app/'s parent directory. A first attempt
at fixing it with import.meta.dirname broke instead, for the same
cross-module-graph reason config-path resolution already documented -
Next compiles Route Handlers through a separate module graph that
doesn't preserve source-relative import.meta paths. Fixed by exposing
the app root via TRIGGERSHELL_APP_ROOT (set once in server.ts, where
import.meta *does* resolve correctly), the same pattern already used
for TRIGGERSHELL_CONFIG_PATH.

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

src/app/api/auth/login/route.ts

@@ -0,0 +1,62 @@
+export const dynamic = "force-dynamic";
+
+import { eq } from "drizzle-orm";
+import { z } from "zod";
+import { getDb } from "@/lib/db/client";
+import { users } from "@/lib/db/schema";
+import { verifyPassword } from "@/lib/auth/password";
+import { getSession } from "@/lib/auth/session";
+import {
+  isRateLimited,
+  recordFailedAttempt,
+  clearAttempts,
+} from "@/lib/auth/rate-limit";
+
+const loginSchema = z.object({
+  username: z.string().min(1),
+  password: z.string().min(1),
+});
+
+export async function POST(request: Request) {
+  const rateLimitKey = request.headers.get("x-forwarded-for") ?? "local";
+  if (isRateLimited(rateLimitKey)) {
+    return Response.json(
+      { error: "Too many attempts, try again later." },
+      { status: 429 },
+    );
+  }
+
+  const body = await request.json().catch(() => null);
+  const parsed = loginSchema.safeParse(body);
+  if (!parsed.success) {
+    return Response.json({ error: "Invalid request body" }, { status: 400 });
+  }
+
+  const db = getDb();
+  const user = db
+    .select()
+    .from(users)
+    .where(eq(users.username, parsed.data.username))
+    .get();
+
+  if (
+    !user ||
+    !(await verifyPassword(user.passwordHash, parsed.data.password))
+  ) {
+    recordFailedAttempt(rateLimitKey);
+    return Response.json({ error: "Invalid credentials" }, { status: 401 });
+  }
+
+  clearAttempts(rateLimitKey);
+  db.update(users)
+    .set({ lastLoginAt: new Date() })
+    .where(eq(users.id, user.id))
+    .run();
+
+  const session = await getSession();
+  session.userId = user.id;
+  session.username = user.username;
+  await session.save();
+
+  return Response.json({ user: { username: user.username } });
+}