feat: config crate with legacy env names

Cargo.toml

@@ -28,6 +28,7 @@ members = [
     "crates/adapters/jellyfin",
     "crates/adapters/plex",
     "crates/infra-wiring",
+    "crates/config",
 ]
 resolver = "2"
 
@@ -63,6 +64,7 @@ hex = "0.4"
 object_store = { version = "0.11", features = ["aws"] }
 axum = { version = "0.8.8", features = ["macros", "multipart"] }
 csv = "1"
+figment = { version = "0.10", features = ["toml", "env"] }
 
 api-types = { path = "crates/api-types" }
 domain = { path = "crates/domain" }
@@ -89,6 +91,7 @@ jellyfin = { path = "crates/adapters/jellyfin" }
 plex = { path = "crates/adapters/plex" }
 image-converter = { path = "crates/adapters/image-converter" }
 infra-wiring = { path = "crates/infra-wiring" }
+config = { path = "crates/config" }
 
 [profile.dev]
 debug = 1                    # line tables only — still debuggable, much faster linking