Drop merged GraphQL schema for split files

Relay no longer needs a single merged schema.graphql: each project in
relay.config.json now reads the split graphql/*.graphql files directly
via `schema` (base.graphql) plus `schemaExtensions`. gqlgen already
consumed the split files, so the merge step only fed Relay and the
optional IDE GraphQL extension.

Remove the merge machinery (contrib/merge-graphql-schema.sh, the
RELAY_SCHEMAS make rules, and the gitignore entry) and drop the
graphql-config files (apps/trust/graphql.config.yml and the root
package.json graphql field); the Relay extension provides schema-aware
language features from relay.config.json on its own.

relay-compiler keeps generated artifacts in sync (stale ones are
removed automatically), so the relay npm script just runs the local
relay-compiler and the make target delegates to it.

Signed-off-by: Émile Ré <emile@probo.com>

package.json

@@ -15,17 +15,12 @@
     "dev": "turbo run dev",
     "lint": "turbo run lint",
     "check": "turbo run check",
-    "relay-clean": "find apps -type d -name __generated__ -exec rm -rf {} +",
-    "relay-compile": "npx relay-compiler",
-    "relay": "npm run relay-clean && npm run relay-compile"
+    "relay": "relay-compiler"
   },
   "devDependencies": {
     "relay-compiler": "^21.0.1",
     "turbo": "^2.9.14"
   },
-  "graphql": {
-    "schema": "./pkg/server/api/console/v1/graphql/"
-  },
   "overrides": {
     "brace-expansion": "^5.0.5",
     "minimatch@3": {