Replace raw print/debugPrint usage with structured, redacted logging

[NihalDR]

Problem

The codebase contains many raw print / debugPrint calls in production paths. This can:

• create noisy logs that make real errors harder to triage
• leak internal state or sensitive runtime details in logs
• make logging behavior inconsistent across modules

Example locations

• lib/app/utils/system_ringtone_service.dart:75
• lib/app/data/providers/push_notifications.dart:8
• lib/app/modules/timer/views/timer_animation.dart:35

Why this is important

Logging should follow a structured policy with controllable verbosity and redaction. Ad-hoc prints increase operational risk and reduce observability quality.

Proposed fix

• Introduce a centralized logging utility (e.g., wrapper with levels: debug/info/warn/error)
• Gate debug-level logs behind build mode / config
• Redact sensitive fields (tokens, user IDs, emails, device-specific identifiers)
• Replace raw print/debugPrint calls incrementally, starting with app logic and providers
• Add lint or CI check to prevent new raw print statements in production code

Acceptance criteria

• Raw print calls removed from production paths (or explicitly justified)
• debugPrint usage follows centralized logger policy
• Sensitive values are redacted in logs
• Developer docs include logging guidelines