fix: allowlist thinkingEffort in SettingsUpdateSchema

Without this, PUT /api/settings rejects the new field with
INVALID_INPUT (schema is .strict()), so the dropdown's value
never persists.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/web/schemas.ts

@@ -267,6 +267,7 @@ export const SettingsUpdateSchema = z
     tunnelEnabled: z.boolean().optional(),
     tabTwoRows: z.boolean().optional(),
     agentTeamsEnabled: z.boolean().optional(),
+    thinkingEffort: z.string().max(20).optional(),
     // UI visibility
     showFontControls: z.boolean().optional(),
     showSystemStats: z.boolean().optional(),