Phase 4: web markers and JourneyMap/Xaero waypoint chat sharing

Linked accounts can place 2D markers on the map (y auto-derived from the
chunk store's heightmap); anonymous visitors keep a localStorage-only
list via the same height lookup. Sharing a marker forwards a structured
payload to the mod over its WS connection, which builds the actual
chat text (see MCMapper-Mod for the JourneyMap/Xaero formatting).

Built test-first per the project's TDD workflow.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015tKdPZt78zbPUZMXWzKEKt

api/src/db/schema.ts

@@ -10,6 +10,10 @@ export const servers = pgTable("servers", {
   // Phase 3: web chat is open to anonymous (unlinked) visitors by default; an admin can require
   // linking per-server. No admin UI to flip this yet (Phase 6) — set directly in the DB for now.
   anonymousChatAllowed: boolean("anonymous_chat_allowed").notNull().default(true),
+  // Phase 4: which format `/mcmapper`-side chat waypoint links are built in when a marker is
+  // shared — 'journeymap' (default), 'xaero', or 'off' to disable sharing entirely. No admin UI
+  // to flip this yet (Phase 6) — set directly in the DB for now, same as anonymousChatAllowed.
+  waypointFormat: text("waypoint_format").notNull().default("journeymap"),
   createdAt: timestamp("created_at", { withTimezone: true }).notNull().defaultNow(),
 });
 
@@ -54,6 +58,28 @@ export const chatMessages = pgTable("chat_messages", {
   createdAt: timestamp("created_at", { withTimezone: true }).notNull().defaultNow(),
 });
 
+// A web-placed marker, owned by a linked account (anonymous visitors keep their marker list in
+// browser localStorage only — see the plan's "Feature: web markers..." section — so there's
+// nothing to persist here for them). Placement is 2D-only (x/z picked on the Leaflet map); `y` is
+// resolved once at creation time from `chunkColumns`' heightmap and stored, not recomputed later,
+// so a marker doesn't silently move if the terrain above it changes afterward.
+export const markers = pgTable("markers", {
+  id: uuid("id").defaultRandom().primaryKey(),
+  accountId: uuid("account_id")
+    .notNull()
+    .references(() => accounts.id, { onDelete: "cascade" }),
+  serverId: uuid("server_id")
+    .notNull()
+    .references(() => servers.id, { onDelete: "cascade" }),
+  dimension: integer("dimension").notNull(),
+  x: integer("x").notNull(),
+  y: integer("y").notNull(),
+  z: integer("z").notNull(),
+  name: text("name").notNull(),
+  color: text("color").notNull(),
+  createdAt: timestamp("created_at", { withTimezone: true }).notNull().defaultNow(),
+});
+
 // Column-granularity world state: the topmost non-air block per (dimension, x, z), plus its
 // height. Kept deliberately separate from `chunkSections` below — cheap to write/read for 2D
 // tile rendering, which never needs full voxel data.