Add initial project structure, including README, CONTRIBUTING, and documentation files

- Created .gitignore to exclude unnecessary files
- Added README.md with project description and core features
- Introduced CONTRIBUTING.md for development guidelines
- Established documentation files for architecture, quality requirements, and technical risks

docs/09_architecture_decisions.md

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+# Architecture Decisions
+
+## ADR-001: Discord.js over Discord.py
+
+**Status:** Accepted  
+**Context:** Node.js and Python both viable. Team has stronger Node.js experience.  
+**Decision:** Use Discord.js for the bot runtime.  
+**Consequences:** Faster development velocity; ecosystem rich with community plugins (command handling, modals, components).
+
+## ADR-002: PostgreSQL over MongoDB
+
+**Status:** Accepted  
+**Context:** Mileage data is relational (user → role → event → score). MongoDB adds flexibility but sacrifices query power.  
+**Decision:** Use PostgreSQL with JSONB columns for extensible user metadata.  
+**Consequences:** Schema migrations needed for new features; joins straightforward.
+
+## ADR-003: Polling over Webhooks for Content Sources
+
+**Status:** Accepted  
+**Context:** YouTube, Instagram, TikTok do not provide push webhooks to arbitrary third parties without approval.  
+**Decision:** Poll public APIs on a CRON schedule (15-min interval).  
+**Consequences:** ~5 min delay between publish and Discord post; API quota management required.
+
+## ADR-004: Modular Monolith over Microservices
+
+**Status:** Accepted  
+**Context:** Single-developer or small team; deployment complexity of microservices not justified.  
+**Decision:** Single process with internal module boundaries (commands, events, mileage, syndication).  
+**Consequences:** Simpler deploy, debug, and develop; can extract services later if needed.