How many sensors can an ARDUINO UNO support?
A arduino can theoretically use more sensors than it has bits of storage based on your lowlever programming and algorithmic skills.
however since most people tend to only use one connection per arduino pin and mostly basic c++ and arduino instructions this is a lot lower. some people also use a shift register to easily increase the port amount.
for your project it depends you can use your ir sensors using one pin each for most ir sensors. the load sensor can be used on a single analog pin if you make it yourself, most prebought ones support ic2 which is really great for your case as I will describe later however you might not need it. hall effect sensor needs one I/O pin, rfid shield seems to use around 5 I/O pins for the average module, and the motor shield you plan to use the lose module which controls 2 motors uses up to 6 I/O pins, the arduino shield might contain more than  L293D motor driver so it might use up more pins, also you should make sure the specific shield edition supports connecting pins to the unused I/O you often have to solder those connections yourself.
so assuming you use all I/O connections and no ic2 where you use one  L293D motor driver board and not a shield(or a shield with pin redirection you should need around:
14 I/O pins from which 1 to a max of 3 are Analog pins(the load and ir ones might be analog based on the type).
however you should check the ports and layout of your actual hardware since this all can differ based on what types you use.
might some of tour sensors use ic2(they have a sda and scl pin) than you need 2 pins on your arduino for all of them together as long as they don't have matching id's. see i2c like a computer network.
so you should be able to use it without a shift register since a arduino uno has 18 basic I/O pins assuming you don't use pin 1 and pin 2 due to the interference with the serial port. 6 of those 18 pins are analog ones. analog pins can be used like normal digital pins. if you use i2c you should also take 2 pins of so you would have 16 usable pins when you use i2c and serial. you can theoretically use 20 pins, but I would recommend not using pin 0 and 1 as for they can prevent your board from accepting a new scetch upload which might require more difficult ways of uploading and problems when using serial connection.