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/comment.py

@@ -0,0 +1,34 @@
+from datetime import datetime, timezone
+from sqlalchemy import String, Integer, DateTime, ForeignKey
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from backend.models.base import Base
+
+
+class Comment(Base):
+    __tablename__ = "comments"
+
+    id: Mapped[int] = mapped_column(primary_key=True)
+    reddit_id: Mapped[str] = mapped_column(String(20), unique=True, nullable=False)
+    post_id: Mapped[int] = mapped_column(ForeignKey("posts.id"), nullable=False, index=True)
+    parent_comment_id: Mapped[int | None] = mapped_column(
+        ForeignKey("comments.id"), index=True
+    )
+    author_id: Mapped[int | None] = mapped_column(ForeignKey("authors.id"), index=True)
+    body: Mapped[str] = mapped_column(nullable=False)
+    score: Mapped[int] = mapped_column(Integer, default=0)
+    created_utc: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False)
+    collected_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), default=lambda: datetime.now(timezone.utc)
+    )
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
+        default=lambda: datetime.now(timezone.utc),
+        onupdate=lambda: datetime.now(timezone.utc),
+    )
+
+    post: Mapped["Post"] = relationship(back_populates="comments")  # noqa: F821
+    author: Mapped["Author | None"] = relationship(back_populates="comments")  # noqa: F821
+    parent_comment: Mapped["Comment | None"] = relationship(
+        remote_side="Comment.id", foreign_keys=[parent_comment_id]
+    )