Add tailwindcss as an explicit dependecy and validate that it exists in user's package.json

[infomiho]

Same issue as #2408

Since Tailwind v4 was released all the Tailwind specific packages that require Tailwind as a peer dep will get the latest (v4) but we only support v3 at the moment. This happens because we don't say explicitly in the user's package.json that we require Tailwind v3.

We should:

• Update Open Saas to include the tailwindcss@^3.2.7 in the package.json Adds tailwindcss as explicit dep open-saas#356
• Update embeddings starter template since it uses Tailwind as well Adds tailwindcss as explicit dep starters#15
• Add validation rules for package.json to require the tailwindcss dep if Tailwind is used Validates tailwindcss if Tailwind is used #2465