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/cli/lib/systemd.ts

@@ -0,0 +1,54 @@
+import os from "node:os";
+import path from "node:path";
+
+export const SERVICE_NAME = "triggershell";
+
+export interface UnitOptions {
+  execPath: string;
+  binPath: string;
+  configPath: string;
+  configDir: string;
+  port?: number;
+  host?: string;
+  scope: "user" | "system";
+}
+
+export function renderUnit(opts: UnitOptions): string {
+  const args = ["start", "--config", opts.configPath, "--no-browser"];
+  if (opts.port !== undefined) args.push("--port", String(opts.port));
+  if (opts.host !== undefined) args.push("--host", opts.host);
+
+  const execStart = [opts.execPath, opts.binPath, ...args]
+    .map((part) => (part.includes(" ") ? `"${part}"` : part))
+    .join(" ");
+
+  const wantedBy = opts.scope === "user" ? "default.target" : "multi-user.target";
+
+  return `[Unit]
+Description=TriggerShell - self-hosted script runner
+After=network.target
+
+[Service]
+Type=simple
+ExecStart=${execStart}
+WorkingDirectory=${opts.configDir}
+Restart=on-failure
+RestartSec=2
+Environment=NODE_ENV=production
+
+[Install]
+WantedBy=${wantedBy}
+`;
+}
+
+export function userUnitPath(): string {
+  return path.join(os.homedir(), ".config", "systemd", "user", `${SERVICE_NAME}.service`);
+}
+
+export function systemUnitPath(): string {
+  return path.join("/etc", "systemd", "system", `${SERVICE_NAME}.service`);
+}
+
+export function isRoot(): boolean {
+  return process.getuid?.() === 0;
+}