fix: scan visibility, NC folder validation, watcher logging

- nc-scan: detailed INFO logging of every path found, subfolder
  contents and skip reasons; 502 now includes the exact folder and
  error so user sees a real message instead of a blank result
- band creation: if nc_base_path is explicitly given, verify the
  folder exists in Nextcloud before saving — returns 422 with a
  clear message to the user; auto-generated paths still do MKCOL
- songs search: add ?unattributed=true to return songs with no
  session_id (files not in a YYMMDD folder)
- BandPage: show "Unattributed Recordings" section below sessions
  so scanned files without a dated folder always appear
- watcher event_loop: promote all per-activity log lines from DEBUG
  to INFO so they're visible in default Docker Compose log output;
  log normalized path and skip reason for every activity

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web/src/pages/BandPage.tsx

@@ -86,6 +86,12 @@ export function BandPage() {
     enabled: !!bandId && tab === "dates",
   });
 
+  const { data: unattributedSongs } = useQuery({
+    queryKey: ["songs-unattributed", bandId],
+    queryFn: () => api.get<SongSummary[]>(`/bands/${bandId}/songs/search?unattributed=true`),
+    enabled: !!bandId && tab === "dates",
+  });
+
   const { data: members } = useQuery({
     queryKey: ["members", bandId],
     queryFn: () => api.get<BandMember[]>(`/bands/${bandId}/members`),
@@ -121,6 +127,7 @@ export function BandPage() {
     mutationFn: () => api.post<NcScanResult>(`/bands/${bandId}/nc-scan`, {}),
     onSuccess: (result) => {
       qc.invalidateQueries({ queryKey: ["sessions", bandId] });
+      qc.invalidateQueries({ queryKey: ["songs-unattributed", bandId] });
       if (result.imported > 0) {
         setScanMsg(`Imported ${result.imported} new song${result.imported !== 1 ? "s" : ""} from ${result.folder} (${result.skipped} already registered).`);
       } else if (result.files_found === 0) {
@@ -404,11 +411,53 @@ export function BandPage() {
                 </span>
               </Link>
             ))}
-            {sessions?.length === 0 && (
+            {sessions?.length === 0 && !unattributedSongs?.length && (
               <p style={{ color: "var(--text-muted)", fontSize: 13 }}>
                 No sessions yet. Scan Nextcloud to import from <code style={{ color: "var(--teal)" }}>{band.nc_folder_path ?? `bands/${band.slug}/`}</code>.
               </p>
             )}
+
+            {/* Songs not linked to any dated session */}
+            {!!unattributedSongs?.length && (
+              <div style={{ marginTop: sessions?.length ? 24 : 0 }}>
+                <div style={{ color: "var(--text-muted)", fontSize: 11, fontFamily: "monospace", letterSpacing: 1, marginBottom: 8 }}>
+                  UNATTRIBUTED RECORDINGS
+                </div>
+                <div style={{ display: "grid", gap: 6 }}>
+                  {unattributedSongs.map((song) => (
+                    <Link
+                      key={song.id}
+                      to={`/bands/${bandId}/songs/${song.id}`}
+                      style={{
+                        background: "var(--bg-inset)",
+                        border: "1px solid var(--border)",
+                        borderRadius: 8,
+                        padding: "14px 18px",
+                        textDecoration: "none",
+                        color: "var(--text)",
+                        display: "flex",
+                        justifyContent: "space-between",
+                        alignItems: "center",
+                        gap: 12,
+                      }}
+                    >
+                      <div style={{ minWidth: 0 }}>
+                        <div style={{ fontWeight: 500, marginBottom: 4 }}>{song.title}</div>
+                        <div style={{ display: "flex", gap: 4, flexWrap: "wrap" }}>
+                          {song.tags.map((t) => (
+                            <span key={t} style={{ background: "var(--teal-bg)", color: "var(--teal)", fontSize: 9, padding: "1px 6px", borderRadius: 3, fontFamily: "monospace" }}>{t}</span>
+                          ))}
+                        </div>
+                      </div>
+                      <span style={{ color: "var(--text-muted)", fontSize: 12, whiteSpace: "nowrap" }}>
+                        <span style={{ background: "var(--bg-subtle)", borderRadius: 4, padding: "2px 6px", marginRight: 8, fontFamily: "monospace", fontSize: 10 }}>{song.status}</span>
+                        {song.version_count} version{song.version_count !== 1 ? "s" : ""}
+                      </span>
+                    </Link>
+                  ))}
+                </div>
+              </div>
+            )}
           </div>
         )}