[eas-cli] Lint the App Store review demo password length

[dennytosp]

Why

Fixes #2785.

apple.review.demoPassword has no length constraint in the metadata schema, so eas metadata:lint passes on a password App Store Connect will reject. The failure only shows up part-way through eas metadata:push, after other entities have already been synced:

x Failed creating store review details for 1.0

Store configuration upload encountered an error.

An attribute value is too long. - Password cannot be longer than 100 characters.

How

Add "maxLength": 100 to demoPassword in packages/eas-cli/schema/metadata-0.json, matching the limit Apple's API enforces, so the lint reports it before the push starts.

Note the App Store Connect web UI caps the field at 50 characters (see the screenshot in #2785), but the API accepts up to 100. Linting to the API limit avoids rejecting configs that push successfully today.

Test Plan

New packages/eas-cli/src/metadata/config/__tests__/validate-test.ts asserts a 100-character password validates and a 101-character one is reported against apple.review.demoPassword.

$ yarn test
Test Suites: 289 passed, 289 total
Tests:       4 skipped, 2444 passed, 2448 total

yarn typecheck, yarn lint (0 warnings), and yarn fmt:check are clean.

[github-actions]

Subscribed to pull request

File Patterns	Mentions
packages/eas-cli/**	@douglowder
packages/eas-cli/schema/**	@byCedric
packages/eas-cli/src/metadata/**	@byCedric

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