refactor: rename configuration variables for clarity

Standardize naming across CLI and server components:
- CLI: serverUrl → apiUrl, HAPI_SERVER_URL → HAPI_API_URL
- Server: webapp* → listen*, miniAppUrl → publicUrl, WEBAPP_* → HAPI_LISTEN_*, WEBAPP_URL → HAPI_PUBLIC_URL
- Rename serverUrlInit.ts → apiUrlInit.ts with updated logic for backward compatibility
- Update all imports, function calls, and documentation accordingly

cli/src/ui/apiUrlInit.ts

@@ -0,0 +1,36 @@
+/**
+ * API URL initialization module
+ *
+ * Handles HAPI_API_URL initialization with priority:
+ * 1. Environment variable (highest - allows temporary override)
+ * 2. Settings file (~/.hapi/settings.json)
+ * 3. Default value (http://localhost:3006)
+ */
+
+import { configuration } from '@/configuration'
+import { readSettings } from '@/persistence'
+
+/**
+ * Initialize API URL
+ * Must be called before any API operations
+ */
+export async function initializeApiUrl(): Promise<void> {
+    // 1. Environment variable has highest priority (allows temporary override)
+    if (process.env.HAPI_API_URL) {
+        return
+    }
+
+    // 2. Read from settings file (new name first, then legacy)
+    const settings = await readSettings()
+    if (settings.apiUrl) {
+        configuration._setApiUrl(settings.apiUrl)
+        return
+    }
+    if (settings.serverUrl) {
+        // Migrate from legacy field name
+        configuration._setApiUrl(settings.serverUrl)
+        return
+    }
+
+    // 3. Default value already set in configuration constructor
+}