Mixed Vegetable Paella

Name: Mixed Vegetable Paella
Ingredients: 5 tablespoons extra-virgin olive oil, divided; 12 ounces squash (such as yellow squash or zucchini), quartered lengthwise and cut into 1/2-inch slices; 1 cup stemmed fresh hen-of-the-woods mushrooms; 1 cup chopped yellow onion; 1 cup chopped red bell pepper; 1 1/2 teaspoons kosher salt, divided; 2 medium garlic cloves, finely chopped; 1/2 cup undrained canned diced tomatoes, or chopped very ripe tomatoes; 2 tablespoons tomato paste; 1 quart vegetable stock or water; Pinch of saffron threads; 1/4 cup thinly sliced Swiss chard; 1 cup uncooked Bomba rice (such as Santo Tomas), see Note; Hot water, as needed; 1/2 medium lemon; 1/4 cup Lemon Aioli; Grilled lemon wedges and cherry tomatoes, for serving; 1/2 cup mayonnaise; 1/2 teaspoon lemon zest; 1/4 teaspoon fresh lemon juice; 1/4 teaspoon grated garlic