fix(deps): relax meta constraint to ^1.15.0 for Flutter 3.24.x-3.37.x compat

[ab1470]

Description

Relax the meta constraint in pubspec.yaml from ^1.17.0 to ^1.15.0 so the SDK resolves cleanly against Flutter 3.24.x–3.37.x, which pin meta via flutter_test (e.g. Flutter 3.35.4 pins meta: 1.16.0).

Fixes MAGE-499 / #79.

Due Diligence

• I have tested this on a simulator/emulator or a physical device, on iOS and Android (if applicable).
• I have added sufficient unit/integration tests of my changes.
• I have adjusted or added new test cases to team test docs, if applicable.
• I am confident these changes are implemented with feature parity across iOS and Android (if applicable).

N/A — dependency-only change. Verified via flutter pub get in the example app.

Release/Versioning Considerations

• Patch Contains internal changes or backwards-compatible bug fixes.
• Minor Contains changes to the public API.
• Major Contains breaking changes.
• Contains readme or migration guide changes.
• This is planned work for an upcoming release.

Changelog / Code Overview

Problem: Flutter 3.24.x–3.37.x pin meta via flutter_test (Flutter 3.24.0 ships meta: 1.15.0; Flutter 3.35.4 ships meta: 1.16.0). Our caret constraint ^1.17.0 rejected those pinned versions, breaking flutter pub get for anyone on Flutter < 3.x-latest.

Fix: Lower the constraint to ^1.15.0.

Why ^1.15.0 is the right floor:

• The SDK only uses the @internal annotation from meta (two sites: klaviyo_native_wrapper.dart:274, klaviyo_sdk.dart:294).
• @internal was introduced in meta 1.3.0 — so any modern version works functionally.
• Flutter 3.24.0 (our declared minimum via flutter: ">=3.24.0") pins meta: 1.15.0 — so ^1.15.0 is the accurate lower bound. Users never pick their own meta version; Flutter pins it transitively.

Test Plan

• flutter pub get in example/ resolves cleanly (was failing with ^1.17.0 on Flutter 3.35.4).
• Reporter (#79) confirms fix on Flutter 3.35.4.

Related Issues/Tickets

• Linear: MAGE-499
• GitHub: #79