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.test.ts

@@ -0,0 +1,35 @@
+import assert from "node:assert/strict";
+import { test } from "node:test";
+import { renderUnit } from "./systemd";
+
+test("renderUnit builds an absolute-path ExecStart with the given args", () => {
+  const unit = renderUnit({
+    execPath: "/usr/bin/node",
+    binPath: "/home/user/.local/share/pnpm/global/5/node_modules/.bin/triggershell",
+    configPath: "/home/user/project/triggershell.yml",
+    configDir: "/home/user/project",
+    port: 8080,
+    host: "0.0.0.0",
+    scope: "user",
+  });
+
+  assert.match(
+    unit,
+    /ExecStart=\/usr\/bin\/node .*triggershell start --config \/home\/user\/project\/triggershell\.yml --no-browser --port 8080 --host 0\.0\.0\.0/,
+  );
+  assert.match(unit, /WorkingDirectory=\/home\/user\/project/);
+  assert.match(unit, /WantedBy=default\.target/);
+});
+
+test("renderUnit uses multi-user.target for the system scope", () => {
+  const unit = renderUnit({
+    execPath: "/usr/bin/node",
+    binPath: "/usr/lib/node_modules/triggershell/bin/triggershell.js",
+    configPath: "/etc/triggershell/triggershell.yml",
+    configDir: "/etc/triggershell",
+    scope: "system",
+  });
+
+  assert.match(unit, /WantedBy=multi-user\.target/);
+  assert.match(unit, /ExecStart=\/usr\/bin\/node .*start --config .*--no-browser$/m);
+});