feat: add dataset export command and contributions views with user stats aggregation

Add dr.dataset console script entry point and implement dump function in new dataset module. Create SQL views for contributions, contributions_extended, rants_of_user, and posts_of_user in db.py to aggregate user activity metrics. Update Makefile with sync, export_stats, and export_dataset targets. Add timeout parameter to HTTP requests in devrant.py and remove demo code. Extend README with usage instructions for environment setup and available dr.* commands.

Makefile

@@ -1,6 +1,16 @@
-all: build
+all: build sync export_stats export_dataset
 
 build:
-	pip install build 
-	python -m build .
-	pip install -e .
+	time pip install build 
+	time python -m build .
+	time pip install -e .
+
+sync:
+	@echo "Synchronizing with devrant.com."
+	time dr.sync
+export_stats:
+	@echo "Exporting statisticts."
+	time dr.stats_all
+export_dataset:
+	@echo "Exporting dataset to be used for LLM embedding."
+	time dr.dataset > export/dataset.txt