feat(notifications): requests and flags reach the people who act on them (#5340)

- A new request still pending after any auto-approval notifies the
  admins (request_pending), but not the requester if they are an admin.
  A request that dedups into one already in flight is not announced again.
- Approving or rejecting a request notifies the requester, and a
  rejection carries the admin's notes as the reason. An admin deciding
  their own request gets nothing.
- The reconciler notifies the requester when their request arrives
  (request_completed), linking the matched album or artist.
- A request the re-acquisition sweeper files and cannot approve itself
  notifies the admins.
- A quarantine flag notifies every admin except the flagger, naming the
  track, the flagger and the reason.

lidarrrequests.Service.CreateTracked reports whether a request was
inserted or deduped; Create wraps it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/api/admin_requests.go

@@ -12,6 +12,7 @@ import (
 	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/lidarr"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/lidarrrequests"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/notifications"
 )
 
 // validRequestStatuses is the set of allowed values for the ?status= param.
@@ -125,6 +126,7 @@ func (h *handlers) handleApproveRequest(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
+	h.notifyRequestDecided(r.Context(), notifications.KindRequestApproved, admin, row, "")
 	h.publishRequestStatusChanged(row)
 	writeJSON(w, http.StatusOK, requestViewFrom(row))
 }
@@ -165,6 +167,7 @@ func (h *handlers) handleRejectRequest(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	h.notifyRequestDecided(r.Context(), notifications.KindRequestRejected, admin, row, body.Notes)
 	h.publishRequestStatusChanged(row)
 	writeJSON(w, http.StatusOK, requestViewFrom(row))
 }