build(rust): declare rust-version 1.88; rustup setup for the server

rust/collector/Cargo.toml

@@ -3,6 +3,7 @@ name = "ping-collector"
 version = "0.1.0"
 description = "Ping River Monitor data collector: RID gauges, HII/ThaiWater, RID dams, Open-Meteo rain -> PostgreSQL"
 edition.workspace = true
+rust-version.workspace = true
 license.workspace = true
 publish.workspace = true
 repository.workspace = true