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>

backend/config.py

@@ -0,0 +1,18 @@
+from pydantic_settings import BaseSettings
+
+
+class Settings(BaseSettings):
+    database_url: str = "postgresql+asyncpg://reddit:changeme@localhost:5432/reddit_monitor"
+    reddit_user_agent: str = "reddit-monitor:v1.0"
+    seed_subreddits: str = ""
+    digest_hour_utc: int = 23
+    ai_summary_enabled: bool = False
+
+    @property
+    def database_url_sync(self) -> str:
+        return self.database_url.replace("+asyncpg", "+psycopg2")
+
+    model_config = {"env_file": ".env", "env_file_encoding": "utf-8"}
+
+
+settings = Settings()