Add WatchEvents, enable/disable/weight RPCs, and config check

gRPC / proto
- Rename WatchBackendEvents → WatchEvents; return a stream of Event
  oneof (LogEvent, BackendEvent, FrontendEvent) with optional filter
  flags (log, log_level, backend, frontend)
- Add EnableBackend, DisableBackend, SetFrontendPoolBackendWeight RPCs
- Rename PauseResumeRequest → BackendRequest
- Add CheckConfig RPC returning ok/parse_error/semantic_error

maglevd
- Route slog through a LogBroadcaster (slog.Handler) so WatchEvents
  subscribers can receive structured log records independently of the
  daemon's own --log-level
- Add --reflection flag (default true) to toggle gRPC server reflection
- Add --check flag: validates config file and exits 0/1/2
- SIGHUP: use config.Check before applying reload; log parse vs semantic
  error separately; refuse reload on any error
- Rename default config path /etc/maglev → /etc/vpp-maglev

maglevc
- Add 'watch events [num <n>] [log [level <level>]] [backend] [frontend]'
  command; prints compact protojson, stops on any keypress or Ctrl-C;
  uses cbreak mode (not raw) so output post-processing is preserved
- Add 'set backend <name> enable|disable'
- Add 'set frontend <name> pool <pool> backend <name> weight <0-100>'
- Add 'config check' command

Debian packaging
- Rename service unit to vpp-maglevd.service
- Rename conffiles to /etc/default/vpp-maglev and /etc/vpp-maglev/
- Create maglevd system user/group in postinst; add to vpp group if present
- Add postrm; add adduser to Depends

debian/build-deb.sh

@@ -22,7 +22,7 @@ install -d "$STAGING/usr/share/man/man1"
 install -d "$STAGING/usr/share/man/man8"
 install -d "$STAGING/lib/systemd/system"
 install -d "$STAGING/etc/default"
-install -d "$STAGING/etc/maglev"
+install -d "$STAGING/etc/vpp-maglev"
 install -d "$STAGING/DEBIAN"
 
 # Binaries
@@ -34,22 +34,23 @@ gzip -9 -c "$REPO_ROOT/docs/maglevd.8" > "$STAGING/usr/share/man/man8/maglevd.8.
 gzip -9 -c "$REPO_ROOT/docs/maglevc.1" > "$STAGING/usr/share/man/man1/maglevc.1.gz"
 
 # Systemd unit
-install -m 644 "$REPO_ROOT/debian/maglevd.service" "$STAGING/lib/systemd/system/maglevd.service"
+install -m 644 "$REPO_ROOT/debian/vpp-maglevd.service" "$STAGING/lib/systemd/system/vpp-maglevd.service"
 
-# /etc/default/maglev  (conffile — dpkg won't overwrite on upgrade)
-install -m 644 "$REPO_ROOT/debian/default.maglev" "$STAGING/etc/default/maglev"
+# /etc/default/vpp-maglev  (conffile — dpkg won't overwrite on upgrade)
+install -m 644 "$REPO_ROOT/debian/default.vpp-maglev" "$STAGING/etc/default/vpp-maglev"
 
-# /etc/maglev/maglev.yaml  (conffile)
-install -m 644 "$REPO_ROOT/debian/maglev.yaml" "$STAGING/etc/maglev/maglev.yaml"
+# /etc/vpp-maglev/maglev.yaml  (conffile)
+install -m 644 "$REPO_ROOT/debian/maglev.yaml" "$STAGING/etc/vpp-maglev/maglev.yaml"
 
 # DEBIAN/control  (version field uses full_version including commit)
 sed "s/@VERSION@/${FULL_VERSION}/;s/@ARCH@/${ARCH}/" \
     "$REPO_ROOT/debian/control.in" > "$STAGING/DEBIAN/control"
 
-# DEBIAN/conffiles, postinst, prerm
+# DEBIAN/conffiles, postinst, prerm, postrm
 install -m 644 "$REPO_ROOT/debian/conffiles" "$STAGING/DEBIAN/conffiles"
 install -m 755 "$REPO_ROOT/debian/postinst"  "$STAGING/DEBIAN/postinst"
 install -m 755 "$REPO_ROOT/debian/prerm"     "$STAGING/DEBIAN/prerm"
+install -m 755 "$REPO_ROOT/debian/postrm"    "$STAGING/DEBIAN/postrm"
 
 # Emit package into build/
 mkdir -p "$REPO_ROOT/build"