Add feed check scheduling, global with per-feed override

general.schedule and feeds.<id>.schedule take "every 30m", "4h", "1d" or
bare minutes. The legacy interval_mins is still read. An explicit per-feed
schedule wins over the publisher's ttl; without one, ttl still raises the
interval when they ask to be polled less often.

Fixes two bugs found while testing it:

null never cleared a field. serde maps JSON null onto the outer None of an
Option<Option<T>>, so "clear this" was indistinguishable from "not
supplied" and every clear silently no-opped with a 204.

The daemon ignored SIGTERM while working. select! races branches only at
selection time, so a signal queued behind an in-flight download and the
process had to be SIGKILLed. The stop signal now cancels work in progress:
SIGTERM mid-download exits in 1s.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RPyeapneuXrCdojsaiXGbe

src/config.rs

@@ -23,8 +23,12 @@ pub struct Config {
 pub struct General {
     pub download_dir: PathBuf,
     pub socket: PathBuf,
-    /// Default poll interval; a feed's own <ttl> wins when it is longer.
-    pub interval_mins: u64,
+    /// How often to re-check feeds: "every 30m", "every 4h", "90" (minutes), "1d".
+    /// A feed's own `schedule` overrides this.
+    pub schedule: String,
+    /// Superseded by `schedule`. Still read so existing configs keep working.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub interval_mins: Option<u64>,
     pub organize: Organize,
     /// 0 = unlimited.
     pub max_total_gb: f64,
@@ -93,6 +97,9 @@ pub struct Feed {
     pub allow_explicit: bool,
     #[serde(default = "yes")]
     pub auto_download: bool,
+    /// Overrides the global schedule for this feed. Same forms: "every 6h", "2d".
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub schedule: Option<String>,
     /// Cap on new downloads per scan. None = unlimited.
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub max_new_per_check: Option<usize>,
@@ -114,7 +121,8 @@ impl Default for General {
         Self {
             download_dir: home().join("Podcasts"),
             socket: default_socket(),
-            interval_mins: 60,
+            schedule: "every 60m".into(),
+            interval_mins: None,
             organize: Organize::Feed,
             max_total_gb: 0.0,
             max_age_days: 0,
@@ -134,6 +142,47 @@ impl Default for Torrent {
     }
 }
 
+impl General {
+    /// Minutes between checks. Falls back to the legacy `interval_mins`, then to an hour.
+    /// A malformed value warns rather than stopping the daemon.
+    pub fn interval(&self) -> u64 {
+        if let Some(n) = parse_interval(&self.schedule) {
+            return n;
+        }
+        if !self.schedule.trim().is_empty() {
+            tracing::warn!(schedule = %self.schedule, "unrecognised schedule; using the default");
+        }
+        self.interval_mins.filter(|n| *n > 0).unwrap_or(60)
+    }
+}
+
+/// Parses a check interval into minutes.
+///
+/// Accepts "every 30m", "30m", "4h", "1d", "every 4 hours", or a bare number of minutes.
+/// Returns None for anything it cannot read, or for zero.
+pub fn parse_interval(s: &str) -> Option<u64> {
+    let s = s.trim().to_lowercase();
+    let s = s.strip_prefix("every").unwrap_or(&s).trim();
+    if s.is_empty() {
+        return None;
+    }
+
+    let digits: String = s.chars().take_while(|c| c.is_ascii_digit()).collect();
+    if digits.is_empty() {
+        return None;
+    }
+    let n: u64 = digits.parse().ok()?;
+    let unit = s[digits.len()..].trim();
+
+    let mins = match unit {
+        "" | "m" | "min" | "mins" | "minute" | "minutes" => n,
+        "h" | "hr" | "hrs" | "hour" | "hours" => n.checked_mul(60)?,
+        "d" | "day" | "days" => n.checked_mul(1440)?,
+        _ => return None,
+    };
+    (mins > 0).then_some(mins)
+}
+
 impl Torrent {
     /// Inclusive listen port range. Falls back to the BitTorrent default on garbage input.
     pub fn ports(&self) -> (u16, u16) {
@@ -273,7 +322,7 @@ mod tests {
         .unwrap();
 
         assert_eq!(cfg.general.download_dir, PathBuf::from("/tmp/pods"));
-        assert_eq!(cfg.general.interval_mins, 60);
+        assert_eq!(cfg.general.interval(), 60);
         assert_eq!(cfg.general.organize, Organize::Feed);
         assert!(cfg.torrent.enabled);
 
@@ -284,6 +333,40 @@ mod tests {
         assert_eq!(feed.keywords, vec!["deep dive"]);
     }
 
+    #[test]
+    fn intervals_parse_from_the_forms_people_actually_type() {
+        for (input, want) in [
+            ("every 30m", 30), ("30m", 30), ("30", 30), ("every 30 minutes", 30),
+            ("every 4h", 240), ("4h", 240), ("4 hours", 240), ("EVERY 4H", 240),
+            ("1d", 1440), ("every 2 days", 2880), ("  every   90m  ", 90),
+        ] {
+            assert_eq!(parse_interval(input), Some(want), "{input:?}");
+        }
+        for bad in ["", "  ", "every", "soon", "-5m", "0", "0h", "every 0 minutes", "5 fortnights"] {
+            assert_eq!(parse_interval(bad), None, "{bad:?} should not parse");
+        }
+    }
+
+    #[test]
+    fn interval_falls_back_through_legacy_then_default() {
+        let mut g = General::default();
+        assert_eq!(g.interval(), 60, "the default schedule");
+
+        g.schedule = "every 15m".into();
+        assert_eq!(g.interval(), 15);
+
+        // A config written before `schedule` existed still works.
+        g.schedule = String::new();
+        g.interval_mins = Some(45);
+        assert_eq!(g.interval(), 45);
+
+        // Garbage must not stop the daemon.
+        g.schedule = "whenever".into();
+        assert_eq!(g.interval(), 45);
+        g.interval_mins = None;
+        assert_eq!(g.interval(), 60);
+    }
+
     #[test]
     fn port_range_falls_back_when_malformed() {
         let mut t = Torrent::default();
@@ -307,7 +390,7 @@ mod tests {
 
         let mut taken = BTreeMap::new();
         taken.insert("the-daily".to_string(), Feed {
-            url: "u".into(), folder: None, keywords: vec![], allow_explicit: false,
+            url: "u".into(), folder: None, schedule: None, keywords: vec![], allow_explicit: false,
             auto_download: true, max_new_per_check: None, username: None,
             password: None, password_env: None,
         });
@@ -319,6 +402,7 @@ mod tests {
         let mut f = Feed {
             url: "https://x/y".into(),
             folder: None,
+            schedule: None,
             keywords: vec![],
             allow_explicit: false,
             auto_download: true,