feat Contests bugfix drive: Tournament Bracket Progression, Creation Fixes & Security

[RsbhThakur]

resolves #43
part of #33

Summary

• Security & Authorization: Enforces server-side isHead authorization for tournament creation and normalizes non-head user payloads to casual 1v1 closed matches. Conforms AuditLog.create calls to AuditLogSchema.
• Timing & Buffer Synchronization: Fixes the fixed +4m start-time validation desync. Casual 1v1 matches require >= 1 min buffer; open tournaments enforce >= (REGISTRATION_DEADLINE_MINUTES + 1) min. Dynamically updates modal quick-add buttons and hint copy.
• Per-Question Scoring & Duration: Adds points and timeLimitMinutes to problem slots and presets. Worker pipeline stamps currentProblemStartTime in Redis on Blitz problem advance and preserves fine-tuned problem points in problem sets.
• Double Elimination Tournament Bracket: Implements Upper, Lower, and Grand Final bracket generation and progression with deterministic Byes, atomic MongoDB room promotions (findOneAndUpdate), and non-blocking Redis key cleanup.
• Interactive Dual-Bracket UI: Adds segmented view filters (All, Upper, Lower, Grand Final) and a dual-tree React Flow layout with drop-down connector lines.
• Unit Tests: Adds comprehensive test suite for bracket position parsing, round naming, snake seeding, and mathematical round distributions.

[ronits2407]

I'll test and review by EOD

[maydayv7]

Alright I'll review later then