Enhance release signing config with robust env handling

[agupta07505]

Description

Initial major release of AttendSmartly v1.0 — an open-source, offline-first Android application designed for college students to track class attendance, compute safe bunks/recovery targets, scan schedules using AI OCR, and manage timetables with custom unit weights.

Key Highlights & Features Included in v1.0:

• Smart Timetable & Flexible Unit Rules: Supports multi-hour and partial unit class sessions with day-by-day scheduling.
• Safe Bunk & Attendance Recovery Calculator: Exact mathematical calculation for safe skippable classes and recovery quotas.
• AI OCR Timetable Scanner: Powered by Google Gemini Vision API to automatically extract timetables from photos.
• Background Alarms & Reminders: Native notification triggers via AlarmManager & WorkManager.
• Jetpack Compose & Material Design 3: Fully responsive, dynamic modern UI supporting dark and light themes.
• Offline Data Backup & CSV Export: SAF-integrated JSON backup/restore and CSV reporting.
• Custom Launcher Icons & Dedicated Website: Brand new transparent launcher icons and official landing website.

Related Issue

Closes #1

Type Of Change

• Bug fix
• New feature
• Breaking change
• Documentation update
• UI/UX improvement
• Refactor
• Test addition or update
• Build/CI release change

App Area

• Timetable Scheduler & Unit Rules
• Safe Bunk & Recovery Calculator
• Attendance History & Session Logs
• Smart Timetable OCR Scanner
• Class Reminders (AlarmManager / WorkManager)
• Data Export / JSON Backups
• Jetpack Compose UI & Material 3 Theming
• Room Database & DataStore Preferences
• CI/CD or Gradle Configuration
• Documentation

Screenshots Or Recordings

Feature
Home Dashboard
Weekly Timetable
Attendance Analytics
AI OCR Scanner

Testing

• ./gradlew testDebugUnitTest
• ./gradlew assembleDebug
• Manual device/emulator testing
• Unit calculation verification (Safe Bunk / Recovery)
• WorkManager / Alarm notification tested, if affected

Checklist

• My code follows the existing project style and architecture.
• I kept the GPL v3 copyright header notice intact in all modified .kt files:
• I added or updated unit tests where useful.
• I updated docs when behavior or features changed.
• I did not commit secrets, API keys, keystores, or generated APKs.