SK-2844 add max file size and max file count support in multi file input element

[skyflow-bharti]

SK-2819: Add maxFileSize and maxFileCount options to MULTI_FILE_INPUT element

Adds two new configurable validation options for MULTI_FILE_INPUT elements, giving developers control over per-file size limits and the maximum number of files that can be selected in a single upload.

Why

The MULTI_FILE_INPUT element previously applied a hard-coded 32 MB size cap and had no limit on the number of files a user could select. There was no way for developers to enforce stricter limits per their product requirements (e.g., a 5 MB cap for profile pictures, or restricting to 2 files per upload). This change exposes maxFileSize and maxFileCount as first-class options on the element so developers can configure these constraints at creation time rather than re-implementing validation outside the SDK.

Goal

maxFileSize: number — validates each selected file against a configurable byte limit. Defaults to 32_000_000 (32 MB). Applies only to MULTI_FILE_INPUT; FILE_INPUT is unaffected.
maxFileCount: number — validates the total number of selected files against a configurable integer limit. Defaults to 4. Applies only to MULTI_FILE_INPUT.
Both options produce specific, user-friendly inline error messages:

• Single file too large → "File exceeds the X MB size limit. Choose a smaller file."
• Named file(s) too large → "<filename(s)> exceeds the X MB size limit. Remove it or choose a smaller file." (all offending filenames are listed)
• Count exceeded → "You can upload up to X files. Remove a file to add a new one."
  Both exceeded simultaneously → "You can upload up to X files, each under Y MB."

Invalid option values (non-positive number, non-integer count) throw a SKYFLOW_ERROR_CODE.INVALID_POSITIVE_NUMBER_OPTIONS error at element creation time.