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/schemas/common.py

@@ -0,0 +1,19 @@
+from datetime import datetime
+from pydantic import BaseModel
+
+
+class PaginationParams(BaseModel):
+    page: int = 1
+    per_page: int = 25
+
+
+class PaginatedResponse(BaseModel):
+    total: int
+    page: int
+    per_page: int
+    pages: int
+
+
+class TimeRangeParams(BaseModel):
+    since: datetime | None = None
+    until: datetime | None = None