Schedule pickers, and target progress at one row

"Check feeds every" becomes a number plus a unit dropdown in both global
and per-feed settings; parse_interval gained weeks to back it. The
per-feed dropdown can select the global default, clearing the override.

Fixes progress painting every pending row: the event carried no enclosure
id, so the handler had nothing to target and set the width on all of them.
Adding a feed looked like it was downloading everything. Progress,
DownloadDone and DownloadError now carry the enclosure id.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AdXho5tTkjFLeUXKbEjKBh

src/ipc.rs

@@ -17,14 +17,17 @@ pub enum Event {
     FeedError { feed: String, msg: String },
     Progress {
         feed: String,
+        /// Which enclosure this is about. Without it a UI cannot tell one download's
+        /// progress from another's and ends up animating every pending row.
+        enclosure: i64,
         url: String,
         file: String,
         done: u64,
         #[serde(skip_serializing_if = "Option::is_none")]
         total: Option<u64>,
     },
-    DownloadDone { feed: String, url: String, path: String, bytes: u64 },
-    DownloadError { feed: String, url: String, msg: String },
+    DownloadDone { feed: String, enclosure: i64, url: String, path: String, bytes: u64 },
+    DownloadError { feed: String, enclosure: i64, url: String, msg: String },
     TorrentDeferred { feed: String, url: String },
     Reaped { path: String, bytes: u64 },
     /// Terminal: a client that asked for work stops reading here.
@@ -252,6 +255,7 @@ mod tests {
     fn events_serialise_to_the_documented_shape() {
         let ev = Event::Progress {
             feed: "atp".into(),
+            enclosure: 42,
             url: "https://x/ep.mp3".into(),
             file: "ep.mp3".into(),
             done: 10_485_760,
@@ -260,10 +264,12 @@ mod tests {
         let json = serde_json::to_string(&ev).unwrap();
         assert!(json.starts_with(r#"{"ev":"progress""#), "got {json}");
         assert!(json.contains(r#""done":10485760"#));
+        assert!(json.contains(r#""enclosure":42"#), "a UI needs this to target one row");
 
         // total is omitted rather than null when the server sent no length.
         let ev = Event::Progress {
             feed: "a".into(),
+            enclosure: 1,
             url: "u".into(),
             file: "f".into(),
             done: 1,