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/post.py

@@ -0,0 +1,42 @@
+from datetime import datetime, timezone
+from sqlalchemy import String, Boolean, Integer, Float, DateTime, ForeignKey, Index
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from backend.models.base import Base
+
+
+class Post(Base):
+    __tablename__ = "posts"
+    __table_args__ = (
+        Index("ix_posts_subreddit_created", "subreddit_id", "created_utc"),
+    )
+
+    id: Mapped[int] = mapped_column(primary_key=True)
+    reddit_id: Mapped[str] = mapped_column(String(20), unique=True, nullable=False)
+    subreddit_id: Mapped[int] = mapped_column(ForeignKey("monitored_subreddits.id"), index=True)
+    author_id: Mapped[int | None] = mapped_column(ForeignKey("authors.id"), index=True)
+    title: Mapped[str] = mapped_column(nullable=False)
+    selftext: Mapped[str | None] = mapped_column()
+    url: Mapped[str | None] = mapped_column()
+    permalink: Mapped[str | None] = mapped_column()
+    flair: Mapped[str | None] = mapped_column(String(255))
+    score: Mapped[int] = mapped_column(Integer, default=0, index=True)
+    upvote_ratio: Mapped[float | None] = mapped_column(Float)
+    num_comments: Mapped[int] = mapped_column(Integer, default=0)
+    is_self: Mapped[bool | None] = mapped_column(Boolean)
+    over_18: Mapped[bool] = mapped_column(Boolean, default=False)
+    hot_rank: Mapped[int | None] = mapped_column(Integer)
+    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),
+    )
+
+    subreddit: Mapped["MonitoredSubreddit"] = relationship(back_populates="posts")  # noqa: F821
+    author: Mapped["Author | None"] = relationship(back_populates="posts")  # noqa: F821
+    comments: Mapped[list["Comment"]] = relationship(back_populates="post")  # noqa: F821
+    metric_snapshots: Mapped[list["MetricSnapshot"]] = relationship(back_populates="post")  # noqa: F821