feat(backend): support container runtime paths

backend/src/config.ts

@@ -1,13 +1,15 @@
 export interface AppConfig {
-  port: number; harnessDir: string; thtBin: string; piBin: string;
+  host: string; port: number; harnessDir: string; thtBin: string; piBin: string;
   authMode: "none" | "mock" | "oidc";
   defaults: { provider?: string; model?: string; thinking?: string };
   maxPiProcesses: number;
   settingsFile: string;
+  dataRoot?: string;
   ollamaEnsureTimeoutMs: number;
 }
 export function loadConfig(env: Record<string, string | undefined>): AppConfig {
   return {
+    host: env.HOST ?? "127.0.0.1",
     port: Number(env.PORT ?? 8787),
     harnessDir: env.THT_HARNESS_DIR ?? "../harness",
     thtBin: env.THT_BIN ?? "tht",
@@ -16,6 +18,7 @@ export function loadConfig(env: Record<string, string | undefined>): AppConfig {
     defaults: { provider: env.PI_PROVIDER, model: env.PI_MODEL, thinking: env.PI_THINKING },
     maxPiProcesses: Number(env.MAX_PI_PROCESSES ?? 4),
     settingsFile: env.SETTINGS_FILE ?? "data/settings.json",
+    dataRoot: env.THT_DATA_ROOT,
     ollamaEnsureTimeoutMs: Number(env.OLLAMA_ENSURE_TIMEOUT_MS ?? 60000),
   };
 }