docs: add infrastructure task tracking and Robot Framework deps

- Rename Docs/Tasks.md → Docs/tasks.md (case fix)
- Add comprehensive task docs for INFRA-1 (server startup) and INFRA-2 (teardown)
- Add test-robot make target
- Add robotframework, browser, requests, jsonlibrary to requirements.txt

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Makefile

@@ -1,4 +1,4 @@
-.PHONY: up down clean browser-clean setup
+.PHONY: up down clean browser-clean setup test-robot
 
 up:
 	python run_server.py
@@ -18,4 +18,7 @@ setup:
 	curl -X POST http://127.0.0.1:8000/setup \
 		-H "Content-Type: application/json" \
 		-H "X-API-Key: 299ae8f630a31bda814263c551361448" \
-		-d '{"path": "/home/lukas/Volume/serien/", "password": "Hallo123!"}'
+		-d '{"path": "/home/lukas/Volume/serien/", "password": "Hallo123!"}'
+
+test-robot:
+	bash tests/robot/run.sh