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/models/author.py

@@ -0,0 +1,23 @@
+from datetime import datetime, timezone
+from sqlalchemy import String, Integer, DateTime
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from backend.models.base import Base
+
+
+class Author(Base):
+    __tablename__ = "authors"
+
+    id: Mapped[int] = mapped_column(primary_key=True)
+    username: Mapped[str] = mapped_column(String(255), unique=True, nullable=False)
+    first_seen_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), default=lambda: datetime.now(timezone.utc)
+    )
+    last_seen_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), default=lambda: datetime.now(timezone.utc)
+    )
+    total_posts: Mapped[int] = mapped_column(Integer, default=0)
+    total_comments: Mapped[int] = mapped_column(Integer, default=0)
+
+    posts: Mapped[list["Post"]] = relationship(back_populates="author")  # noqa: F821
+    comments: Mapped[list["Comment"]] = relationship(back_populates="author")  # noqa: F821