feat(setup): collect server base URL during first-run wizard

Add a Server URL field to the admin-account step of the setup wizard so
the public base URL (used for device sync, OPDS feed, and API endpoints)
is configured up front instead of requiring a later visit to admin
settings.

- setup.templ: base URL input on the admin step plus a summary entry
- setup.ts: default baseUrl to window.location.origin and persist it via
  PUT /system/config ({ base_url }) right after the admin account is
  created, with a non-fatal warning if the save fails

templates/setup.templ

@@ -49,6 +49,19 @@ templ Setup() {
 					<p class="mb-6" style="color: var(--text-secondary)">This first account will have full admin privileges.</p>
 
 					<form @submit.prevent="submitAdmin()">
+						<div class="mb-6 p-4 rounded-lg border" style="background-color: var(--bg-primary); border-color: var(--border)">
+							<label class="block text-sm font-medium mb-1" style="color: var(--text-secondary)">Server URL (Base URL)</label>
+							<input
+								type="url"
+								x-model="admin.baseUrl"
+								placeholder="https://books.example.com"
+								class="w-full px-3 py-2 border rounded mt-2"
+								style="background-color: var(--bg-secondary); color: var(--text-primary); border-color: var(--border)"
+								required
+							/>
+							<p class="text-sm mt-2" style="color: var(--text-secondary)">The public URL of your Bookhoard instance. Used for device sync, OPDS feed, and API endpoints.</p>
+						</div>
+
 						<div class="mb-4">
 							<label class="block text-sm font-medium mb-1" style="color: var(--text-secondary)">Email</label>
 							<input
@@ -289,6 +302,10 @@ templ Setup() {
 
 					<!-- Summary -->
 					<div class="space-y-3 mb-6">
+						<div class="p-4 rounded-lg border" style="background-color: var(--bg-primary); border-color: var(--border)">
+							<p class="text-sm font-medium mb-1" style="color: var(--text-secondary)">Server URL</p>
+							<p style="color: var(--text-primary)" x-text="admin.baseUrl"></p>
+						</div>
 						<div class="p-4 rounded-lg border" style="background-color: var(--bg-primary); border-color: var(--border)">
 							<p class="text-sm font-medium mb-1" style="color: var(--text-secondary)">Administrator</p>
 							<p style="color: var(--text-primary)" x-text="admin.username + ' (' + admin.email + ')'"></p>

web/src/setup.ts

@@ -36,14 +36,13 @@ function initSetup(): void {
   if (savedTheme && savedTheme !== "tokyo-night") {
     applyTheme(savedTheme);
   }
-}
-
-Alpine.data("setupWizard", () => ({
+}Alpine.data("setupWizard", () => ({
   currentStep: 1 as number,
   loading: false as boolean,
   errorMsg: "" as string,
 
   admin: {
+    baseUrl: "",
     email: "",
     username: "",
     password: "",
@@ -71,6 +70,7 @@ Alpine.data("setupWizard", () => ({
 
   init() {
     initSetup();
+    this.admin.baseUrl = window.location.origin;
     setTimeout(() => {
       initPasswordValidation();
     }, 100);
@@ -128,6 +128,8 @@ Alpine.data("setupWizard", () => ({
       setToken(data.token || data.access_token);
       setRefreshToken(data.refresh_token);
 
+      await this.saveBaseUrl();
+
       showToast("Admin account created successfully!", "success");
       this.currentStep = 2;
     } catch (err) {
@@ -137,6 +139,17 @@ Alpine.data("setupWizard", () => ({
     }
   },
 
+  async saveBaseUrl() {
+    if (!this.admin.baseUrl) return;
+    try {
+      await handleVoidResponse(
+        await apiPut("/system/config", { base_url: this.admin.baseUrl })
+      );
+    } catch {
+      showToast("Warning: could not save server URL. You can set it later in Admin Settings.", "warning");
+    }
+  },
+
   async addLibrary() {
     this.clearError();
     this.loading = true;