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/services/comment_service.py

@@ -0,0 +1,57 @@
+from datetime import datetime
+from sqlalchemy import select, func
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from backend.models.comment import Comment
+from backend.models.post import Post
+from backend.models.author import Author
+
+
+async def list_comments(
+    db: AsyncSession,
+    post_id: int | None = None,
+    subreddit_id: int | None = None,
+    author: str | None = None,
+    sort_by: str = "created_utc",
+    sort_order: str = "desc",
+    since: datetime | None = None,
+    until: datetime | None = None,
+    page: int = 1,
+    per_page: int = 25,
+) -> tuple[list[dict], int]:
+    base = select(Comment, Author.username).outerjoin(Author).join(Post)
+
+    filters = []
+    if post_id:
+        filters.append(Comment.post_id == post_id)
+    if subreddit_id:
+        filters.append(Post.subreddit_id == subreddit_id)
+    if author:
+        filters.append(Author.username == author)
+    if since:
+        filters.append(Comment.created_utc >= since)
+    if until:
+        filters.append(Comment.created_utc <= until)
+
+    if filters:
+        base = base.where(*filters)
+
+    count_stmt = select(func.count()).select_from(base.subquery())
+    total = (await db.execute(count_stmt)).scalar() or 0
+
+    sort_col = getattr(Comment, sort_by, Comment.created_utc)
+    if sort_order == "asc":
+        base = base.order_by(sort_col.asc())
+    else:
+        base = base.order_by(sort_col.desc())
+
+    base = base.offset((page - 1) * per_page).limit(per_page)
+
+    result = await db.execute(base)
+    comments = []
+    for comment, author_name in result.all():
+        data = {c.name: getattr(comment, c.name) for c in comment.__table__.columns}
+        data["author_name"] = author_name
+        comments.append(data)
+
+    return comments, total