feat: Flutter SDK update for version 27.1.0-rc.3

[ArnabChatterjee20k]

This PR contains updates to the SDK for version 27.1.0-rc.3 (release candidate).

What's Changed

• Added: background push notifications render the server notification title, body, and image
• Added: requestNotificationPermission() on the Push service
• Added: the SDK requests Android 13+ POST_NOTIFICATIONS itself on first background subscribe
• Fixed: a server-sent title dedupes to one notification per topic instead of one per subscription

[hansi-codes]

🟢 Tier S · Ready to merge

Updates the Flutter SDK to 27.1.0-rc.3 and adds parsing of server-provided notification content. Android gains automatic notification permission requests and image rendering, while web and foreground notifications use the server title and body.

Verdict	New comments	Fixed	Still open
✅ Approved	0	0	0

📂 Walkthrough · 11

File	Change
CHANGELOG.md	Documents notification rendering, permission requests, and title deduplication.
README.md	Updates the dependency version and describes automatic Android permission requests.
android/build.gradle	Bumps the native package version.
android/src/main/kotlin/io/appwrite/flutter/AppwritePushPlugin.kt	Tracks the attached Activity and handles notification permission requests.
android/src/main/kotlin/io/appwrite/services/PushBackground.kt	Parses notification content, deduplicates server titles, and downloads notification images.
lib/src/client_browser.dart, lib/src/client_io.dart	Updates the SDK version sent in request headers.
lib/src/mqtt_browser.dart	Uses server notification content and deduplicates notification titles.
lib/src/mqtt_foreground.dart	Uses server-provided notification titles and bodies.
lib/src/mqtt_io.dart, lib/src/mqtt_native.dart	Requests Android notification permission when hosting background subscriptions.
lib/src/mqtt_notification.dart	Adds shared Dart parsing and fallback rules for notification content.
pubspec.yaml	Bumps the package version to 27.1.0-rc.3.

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[hansi-codes]

🔵 Tier A · Looks good to merge. Summary