feat: add PDF encryption, viewer output actions, and compact minimap

[Chethan616]

Summary

• Add Encrypt PDF using the existing PDFBox security layer.
• Add symmetric View PDF actions for selected, encrypted, and unlocked outputs.
• Keep password-protected PDF opening inside the viewer password flow.
• Improve the viewer minimap/page scrubber with a compact glass rail, page ticks, smaller preview, and tighter spacing.
• Include the signature recolor fix, named signature prompt, Portuguese/i18n updates, and onboarding redesign already in this branch.
• Document third-party licenses in THIRD_PARTY_NOTICES.md.

Validation

• ./gradlew.bat :app:assembleRelease passes.
• git diff --check passes.
• Live ADB smoke testing was attempted, but the connected device disconnected during installation and needs to reconnect for tap-through verification.

Please review and merge manually when ready.

[gitguardian]

⚠️ GitGuardian has uncovered 1 secret following the scan of your pull request.

Please consider investigating the findings and remediating the incidents. Failure to do so may lead to compromising the associated services or software components.

🔎 Detected hardcoded secret in your pull request

GitGuardian id	GitGuardian status	Secret	Commit	Filename
35942260	Triggered	Generic Password	e9d435f	app/src/main/java/com/chethan616/clearpdf/ui/viewmodel/PdfViewerViewModel.kt	View secret

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