Use one name for each thing the UI shows (closes #399)

The UI gave one thing several names. The `database` type is now Archive in the type list, on its badge and on the edit page, and its settings read "Archive expiry" and "Archive rotation" everywhere. The retry field is "Delivery attempts", with help text, errors and the target list saying it counts every attempt; a stored 0 shows as one attempt. The target list uses one capitalisation. The navbar says "Sign out", the sign-in page "Sign in", and the resubmit notice "webhook" instead of "source". The README follows. Stored values, their meaning, routes and form field names are unchanged.

Model: opus-5-5

internal/handlers/target_edit_test.go

@@ -418,6 +418,30 @@ func TestHandleTargetEdit_PrefillsTheStoredValuesUnmasked(
 	assert.Contains(t, page, "original-name")
 }
 
+// TestHandleTargetEdit_CallsTheDatabaseTypeArchive pins the names the
+// edit page of a database target gives its type and its settings to
+// the ones its badge and the add target form use.
+func TestHandleTargetEdit_CallsTheDatabaseTypeArchive(t *testing.T) {
+	t.Parallel()
+
+	env := setupSourceTest(t)
+	webhook := seedWebhookWithRetention(t, env.db, 30)
+	target := seedTarget(t, env.db, webhook.ID, database.TargetTypeDatabase)
+
+	w := serveTarget(
+		env, http.MethodGet,
+		"/hook/"+webhook.ID+"/targets/"+target.ID+"/edit",
+		nil,
+	)
+	require.Equal(t, http.StatusOK, w.Code)
+
+	page := w.Body.String()
+
+	assert.Contains(t, page, "Type: archive.")
+	assert.Contains(t, page, `class="label">Archive expiry</label>`)
+	assert.Contains(t, page, `class="label">Archive rotation</label>`)
+}
+
 // TestHandleTargetEditSubmit_Rejects covers every submission that
 // must not reach storage.
 //
@@ -588,7 +612,7 @@ func TestHandleTargetEditSubmit_RefusedFormComesBack(t *testing.T) {
 		{
 			database.TargetTypeSlack,
 			"name=edited&url=" + editOriginalURL + "&max_retries=25",
-			"Invalid max retries",
+			"Invalid delivery attempts",
 		},
 		{
 			database.TargetTypeDatabase,