refactor(events): expand eventType taxonomy with central config

Replaces the four-value enum (community/workshop/social/showcase) with
seven values: talk, workshop, community-meetup, coworking, peer-session,
skills-share, info-session. Default is now community-meetup.

Adds app/config/eventTypes.js as the single source of truth for value→label
mapping. Updates the model enum, seed scripts, and admin event list/filter
+ admin dashboard to read from it via EVENT_TYPES and eventTypeLabel().

server/models/event.js

@@ -15,8 +15,16 @@ const eventSchema = new mongoose.Schema({
   endDate: { type: Date, required: true },
   eventType: {
     type: String,
-    enum: ["community", "workshop", "social", "showcase"],
-    default: "community",
+    enum: [
+      "talk",
+      "workshop",
+      "community-meetup",
+      "coworking",
+      "peer-session",
+      "skills-share",
+      "info-session",
+    ],
+    default: "community-meetup",
   },
   // IANA timezone for interpreting datetime input and rendering the event time.
   displayTimezone: { type: String, default: "America/Toronto" },