Add Reddit monitoring bot — backend, frontend, and Docker config

Python/FastAPI backend with PostgreSQL for collecting Reddit data via
public .json endpoints. React/Vite dashboard for analytics. Docker Compose
setup with API and worker services connecting to shared PostgreSQL.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.env.example

@@ -0,0 +1,14 @@
+# Database (shared PostgreSQL instance)
+DATABASE_URL=postgresql+asyncpg://reddit:changeme@localhost:5432/reddit_monitor
+
+# Reddit scraping
+REDDIT_USER_AGENT=reddit-monitor:v1.0
+
+# Subreddits to auto-add on first worker startup (comma-separated)
+SEED_SUBREDDITS=
+
+# Daily digest generation hour (UTC, 0-23)
+DIGEST_HOUR_UTC=23
+
+# AI summaries (stub — enable later)
+AI_SUMMARY_ENABLED=false