Upgrade Relay to v20.1.1 and unify compiler config

Consolidate the two per-app relay configs (console and trust)
into a single multi-project relay.config.json at the repo root
with three projects: core, iam, and trust. Bump all relay
packages from v19 to v20.1.1 and move relay-compiler to the
root devDependencies. Replace per-workspace relay scripts with
a single root-level npm run relay command and update the
GNUmakefile, CI workflows, and docs accordingly.

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

packages/routes/package.json

@@ -16,8 +16,8 @@
   },
   "peerDependencies": {
     "react": "^19.2.1",
-    "react-relay": "^19.0.0",
+    "react-relay": "^20.1.1",
     "react-router": "^7.10.0",
-    "relay-runtime": "^19.0.0"
+    "relay-runtime": "^20.1.1"
   }
 }