libraries: initial availability sweep before watcher's first sleep

new_health_map seeds every library as Online, and the watcher's tick
loop sleeps WATCH_QUICK_INTERVAL_SECONDS (default 60s) before its
first probe — meaning /libraries reported the optimistic default for
up to a minute after boot, even when a share was clearly unmounted.

Run the same refresh_health pass once at the top of the watcher
thread before entering the sleep loop. /libraries is then truthful
within milliseconds of the watcher thread starting (effectively from
the first HTTP request, since the watcher spawns well before the
server binds).

The per-tick gate inside the loop is unchanged.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/main.rs

@@ -1945,6 +1945,24 @@ fn watch_files(
         let mut last_full_scan = SystemTime::now();
         let mut scan_count = 0u64;
 
+        // Initial availability sweep before the loop's first sleep so
+        // /libraries reports the truth from the very first request,
+        // rather than the optimistic Online default that
+        // new_health_map seeds. Without this, an unmounted share would
+        // appear online for up to WATCH_QUICK_INTERVAL_SECONDS (default
+        // 60s) after boot. Same probe logic as the per-tick gate
+        // below; no ingest runs here, just the health update + log.
+        for lib in &libs {
+            let context = opentelemetry::Context::new();
+            let had_data = exif_dao
+                .lock()
+                .expect("exif_dao poisoned")
+                .count_for_library(&context, lib.id)
+                .map(|n| n > 0)
+                .unwrap_or(false);
+            libraries::refresh_health(&library_health, lib, had_data);
+        }
+
         loop {
             std::thread::sleep(Duration::from_secs(quick_interval_secs));