Adds a URL input + Subscribe button (dx-components Input/Button) to the
UI, wired to a new subscribe_feed server function that upserts the feed
row and does an immediate first fetch so the reader isn't empty until
the next scheduled poll. feedsignal_feeds::fetch_feed now also returns
the feed's title, used to replace the URL placeholder once fetched.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XJJQb2DWZZwQ1yPiaAQQoY

@@ -40,0 +73,4 @@
+    rsx! {
+        form {
+            class: "subscribe-form",
+            onsubmit: move |ev| {

@@ -9,3 +10,4 @@
     let bytes = reqwest::get(feed_url).await?.bytes().await?;
     let parsed = feed_rs::parser::parse(&bytes[..])?;
 
+    let title = parsed

@@ -40,0 +52,4 @@
+
+    let submit = move |_| {
+        let feed_url = url.read().clone();
+        if feed_url.trim().is_empty() {

@@ -12,0 +14,4 @@
+        .title
+        .as_ref()
+        .map(|t| t.content.clone())
+        .filter(|t| !t.trim().is_empty())

@@ -71,0 +72,4 @@
+/// already subscribed) and does an immediate first fetch so the reader
+/// isn't empty until the next scheduled poll. Returns the number of
+/// articles pulled in on this fetch.
+pub async fn subscribe_feed_impl(db: Db, url: String) -> Result<usize> {

@@ -71,0 +74,4 @@
+/// articles pulled in on this fetch.
+pub async fn subscribe_feed_impl(db: Db, url: String) -> Result<usize> {
+    let url = url.trim();
+    anyhow::ensure!(!url.is_empty(), "feed URL is required");

@@ -71,0 +76,4 @@
+    let url = url.trim();
+    anyhow::ensure!(!url.is_empty(), "feed URL is required");
+
+    // Register under a placeholder title first so the feed exists even if

@@ -54,0 +77,4 @@
+    /// A blank or whitespace-only feed title should be treated the same as
+    /// a missing one, not surfaced as an empty string in the UI.
+    #[test]
+    fn has_content_rejects_blank_strings() {