refactor: detach yarn prisma generate from yarn-install action (#26382)

* refactor: detach yarn prisma generate from yarn-install action

Co-Authored-By: keith@cal.com <keithwillcode@gmail.com>

* fix: add run-prisma-generate input for backward compatibility

The yarn-install action now has a run-prisma-generate input that defaults
to true for backward compatibility. This ensures CI works correctly since
workflow files are pulled from the base branch (main) while actions are
pulled from the PR branch.

Workflows that have explicit yarn prisma generate steps now set
run-prisma-generate: false to avoid running it twice after merge.

Co-Authored-By: keith@cal.com <keithwillcode@gmail.com>

* refactor: completely remove prisma generate from yarn-install action

Remove all prisma-related code from the yarn-install action:
- Remove the run-prisma-generate input parameter
- Remove the Generate Prisma client step

Remove explicit yarn prisma generate steps from all workflow files.

Prisma generation is now handled by the postinstall script in package.json
which runs 'turbo run post-install' after yarn install. This triggers
@calcom/prisma#post-install which runs 'prisma generate && prisma format'.

This makes the yarn-install action have no knowledge of Prisma at all,
as requested.

Co-Authored-By: keith@cal.com <keithwillcode@gmail.com>

* fix: add generic post-install step to ensure generated files are up-to-date

When all caches are hit, yarn install completes quickly without running
the postinstall script. This means generated files (like Prisma types)
may not be created.

Add a generic 'turbo run post-install' step that runs after yarn install
to ensure all post-install tasks complete regardless of cache state.
This keeps the action from having Prisma-specific knowledge while
ensuring the post-install pipeline runs.

Co-Authored-By: keith@cal.com <keithwillcode@gmail.com>

* refactor: remove post-install step from yarn-install action

Remove the turbo run post-install step as requested. The yarn-install
action now only handles yarn install with caching, with no knowledge
of post-install tasks or Prisma generation.

Let CI show what fails without explicit post-install handling.

Co-Authored-By: keith@cal.com <keithwillcode@gmail.com>

* Add back Prisma schema loaded from schema.prisma

✔ Generated Prisma Client (6.16.1) to ./generated/prisma in 442ms

✔ Generated Zod Prisma Types to ./zod in 1.43s

✔ Generated Kysely types (2.2.0) to ./../kysely in 271ms

✔ Generated Prisma Enum Generator to ./enums/index.ts in 176ms where needed

* Adding Prisma schema loaded from schema.prisma

✔ Generated Prisma Client (6.16.1) to ./generated/prisma in 451ms

✔ Generated Zod Prisma Types to ./zod in 1.40s

✔ Generated Kysely types (2.2.0) to ./../kysely in 271ms

✔ Generated Prisma Enum Generator to ./enums/index.ts in 205ms where needed for E2E

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Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>