Show the running version on Settings > General

The General page ends with a Version block naming the release this
server runs, so an update can be confirmed from the app.

The version is COBBLE_VERSION, the release tag the image was built with
(Dockerfile ARG, passed by the release workflow, which falls back to
package.json's version on a workflow-dispatch build), else package.json's
version, which a development server reports too, with (development)
after it. runningVersion (src/utils/running-version.ts) drops an
unusable version string rather than showing it.

Also includes the working tree's pending signup guard in
src/pages/__root.server.ts: a user who still holds a session while the
install has no users is sent to /auth/logout (and may load it).

src/utils/running-version.test.ts

@@ -0,0 +1,64 @@
+import { describe, expect, test } from "bun:test";
+import runningVersion from "./running-version";
+
+describe("runningVersion", () => {
+    test("a release reports the build's version", () => {
+        expect(
+            runningVersion({
+                env: { NODE_ENV: "production", COBBLE_VERSION: "v0.1.1" },
+            }),
+        ).toEqual({ version: "v0.1.1", mode: "production" });
+    });
+
+    test("a production build without a version falls back to the source's", () => {
+        expect(
+            runningVersion({
+                env: { NODE_ENV: "production" },
+                package_version: "0.1.1",
+            }),
+        ).toEqual({ version: "0.1.1", mode: "production" });
+    });
+
+    test("a development server reports the source's version too", () => {
+        expect(
+            runningVersion({
+                env: { NODE_ENV: "development" },
+                package_version: "0.1.1",
+            }),
+        ).toEqual({ version: "0.1.1", mode: "development" });
+    });
+
+    test("a development server with a build version prefers it", () => {
+        expect(
+            runningVersion({
+                env: { NODE_ENV: "development", COBBLE_VERSION: "v0.2.0" },
+                package_version: "0.1.1",
+            }),
+        ).toEqual({ version: "v0.2.0", mode: "development" });
+    });
+
+    test("no NODE_ENV at all is a development server", () => {
+        expect(runningVersion({ env: {}, package_version: "0.1.1" })).toEqual({
+            version: "0.1.1",
+            mode: "development",
+        });
+    });
+
+    test("an unusable version is dropped rather than shown", () => {
+        expect(
+            runningVersion({
+                env: { NODE_ENV: "production", COBBLE_VERSION: "bad version!" },
+                package_version: "",
+            }),
+        ).toEqual({ version: null, mode: "production" });
+    });
+
+    test("an empty build version falls back to the source's", () => {
+        expect(
+            runningVersion({
+                env: { NODE_ENV: "production", COBBLE_VERSION: "  " },
+                package_version: "0.1.1",
+            }),
+        ).toEqual({ version: "0.1.1", mode: "production" });
+    });
+});