security: .gitignore missing critical entries for API keys and signing credentials

[SISIR-REDDY]

Description

The current .gitignore does not protect against accidentally committing sensitive files:

Missing Entries

File	Risk
android/app/google-services.json	Firebase API keys for Android
ios/Runner/GoogleService-Info.plist	Firebase API keys for iOS
android/key.properties	Android release signing passwords
*.jks / *.keystore	Android signing keystores
.env.local / .env.production	Production API keys

Current .gitignore

The current file only has the default Flutter template entries. It ignores .env but not .env.local, .env.production, or any Firebase/signing credential files.

Impact

Any contributor who adds Firebase or configures release signing could accidentally push API keys or signing credentials to the public repo.

Expected Fix

Add security-critical exclusions to .gitignore.