Self-hosted APK distribution

Memby is handed out from a NAS or web server rather than a store, so:

- UpdateChecker gains a static-manifest source alongside Gitea. A .json
  update URL is read as a manifest ({version, apkUrl, notes}); anything
  else is still treated as a Gitea host. apkUrl may be relative and is
  resolved against the manifest's own URL.
- Release signing config reads memby.keystore from local.properties or
  the environment. Without it the build still succeeds but warns loudly:
  an unsigned APK will not install, and a changed key forces every user
  to uninstall before they can update.
- release.ps1 bumps the version, runs tests, builds a signed APK and
  assembles dist/out/ (landing page, latest.json, versioned APK) ready to
  copy onto the NAS.
- Keystores and dist/out are gitignored.

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

app/src/test/java/com/ponzischeme89/memby/update/UpdateSourceTest.kt

@@ -0,0 +1,76 @@
+package com.ponzischeme89.memby.update
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+/**
+ * The update source is chosen by URL shape, and a manifest's apkUrl may be relative.
+ * Both are easy to get subtly wrong and would strand every TV on an old build.
+ */
+class UpdateSourceTest {
+
+    @Test
+    fun `a json url is a static manifest`() {
+        assertTrue(isManifestUrl("https://nas.example.com/memby/latest.json"))
+        assertTrue(isManifestUrl("https://nas.example.com/memby/latest.JSON"))
+        assertTrue(isManifestUrl("https://nas.example.com/memby/latest.json?v=2"))
+    }
+
+    @Test
+    fun `a bare host is treated as gitea`() {
+        assertFalse(isManifestUrl("https://g.sublogue.com"))
+        assertFalse(isManifestUrl("https://g.sublogue.com/"))
+        // A folder that merely contains json elsewhere is not a manifest.
+        assertFalse(isManifestUrl("https://nas.example.com/json"))
+    }
+
+    @Test
+    fun `an absolute apk url is used as-is`() {
+        val resolved = resolveApkUrl(
+            "https://nas.example.com/memby/latest.json",
+            "https://cdn.example.com/memby-0.1.54.apk",
+        )
+        assertEquals("https://cdn.example.com/memby-0.1.54.apk", resolved)
+    }
+
+    @Test
+    fun `a relative apk url resolves next to the manifest`() {
+        val resolved = resolveApkUrl(
+            "https://nas.example.com/memby/latest.json",
+            "memby-0.1.54.apk",
+        )
+        assertEquals("https://nas.example.com/memby/memby-0.1.54.apk", resolved)
+    }
+
+    @Test
+    fun `a root-relative apk url keeps the host`() {
+        val resolved = resolveApkUrl(
+            "https://nas.example.com/memby/latest.json",
+            "/downloads/memby-0.1.54.apk",
+        )
+        assertEquals("https://nas.example.com/downloads/memby-0.1.54.apk", resolved)
+    }
+
+    @Test
+    fun `a query string on the manifest does not leak into the apk url`() {
+        val resolved = resolveApkUrl(
+            "https://nas.example.com/memby/latest.json?nocache=1",
+            "memby-0.1.54.apk",
+        )
+        assertEquals("https://nas.example.com/memby/memby-0.1.54.apk", resolved)
+    }
+
+    @Test
+    fun `manifest decodes with the field names the release script writes`() {
+        val json = kotlinx.serialization.json.Json { ignoreUnknownKeys = true }
+        val manifest = json.decodeFromString<UpdateManifest>(
+            """{"version":"0.1.54","apkUrl":"memby-0.1.54.apk","notes":"Faster home screen"}""",
+        )
+
+        assertEquals("0.1.54", manifest.version)
+        assertEquals("memby-0.1.54.apk", manifest.apkUrl)
+        assertEquals("Faster home screen", manifest.notes)
+    }
+}