Fix M3U write permission failure; add recently-downloaded section to dashboard

Playlist M3U regen now writes to a temp file and renames it into place,
so a stray wrong-owner leftover file (root:root, from pre-migration
host-cron runs) can't block nightly writes the way it did last night.
Dashboard now lists tracks added to the beets library in the last 24h
with playlist and format, sourced from a new beets_service.recently_added().

app/routers/dashboard.py

@@ -1,3 +1,5 @@
+import time
+
 from fastapi import APIRouter, Depends, Request
 from fastapi.templating import Jinja2Templates
 from sqlalchemy import select
@@ -10,6 +12,8 @@ from app.services import beets_service, credential_service, playlist_service
 router = APIRouter(tags=["dashboard"])
 templates = Jinja2Templates(directory="app/templates")
 
+_RECENT_TRACKS_WINDOW_SECONDS = 24 * 60 * 60
+
 
 def _human_bytes(n: int) -> str:
     size = float(n)
@@ -27,6 +31,7 @@ async def dashboard(request: Request, user: dict = Depends(require_auth), db=Dep
     recent_runs = list(
         db.execute(select(JobRun).order_by(JobRun.started_at.desc()).limit(10)).scalars()
     )
+    recent_tracks = beets_service.recently_added(time.time() - _RECENT_TRACKS_WINDOW_SECONDS)
     return templates.TemplateResponse(
         request,
         "dashboard.html",
@@ -37,6 +42,7 @@ async def dashboard(request: Request, user: dict = Depends(require_auth), db=Dep
             "playlist_count": len(playlists),
             "active_playlist_count": len([p for p in playlists if p.active]),
             "recent_runs": recent_runs,
+            "recent_tracks": recent_tracks,
             "auth_states": credential_service.auth_states(db),
         },
     )