meteor3: raven -> @sentry/node + @sentry/browser

flowkey:raven (Sentry legacy SDK) is dead on Meteor 3 and, with the old
sentry.comunes.org DSN unreachable, spammed the boot log with 502s on every
exception. Replaced by the modern SDKs (8.x) behind the same ravenLogger.log()
facade so the 6 call sites are unchanged. Empty DSN -> plain console logger
(same behavior as before).

End-to-end verified against a real backend: GlitchTip deployed on aaron
(Sentry-compatible, fits in ~1.5GB vs Sentry's 16GB), fronted at
sentry.comunes.org. A test exception sent from the dev server appeared in
GlitchTip within seconds. REST smoke byte-identical (12/12).

.meteor/packages

@@ -35,7 +35,6 @@ alexwine:bootstrap-4
 gadicc:blaze-react-component  # Add braze to react
 255kb:meteor-status           # Connect status
 # mixmax:smart-disconnect       # Disconnect on lost focus (disabled to get notif)
-flowkey:raven                 # js errors
 vjrj:piwik                    # Stats
 mdg:geolocation
 tcef:publish-performant-counts

.meteor/versions

@@ -42,7 +42,6 @@ es5-shim@4.8.1
 facebook-oauth@1.11.4
 facts-base@1.0.2
 fetch@0.1.5
-flowkey:raven@1.1.0
 fortawesome:fontawesome@4.7.0
 fourseven:scss@5.0.0
 gadicc:blaze-react-component@2.0.1