Sprint 1: Add libs/README.md with download instructions for httplib.h and json.hpp

libs/README.md

@@ -0,0 +1,24 @@
+# Required Libraries (download once)
+
+These are header-only libraries. Download them into this directory:
+
+## httplib.h (cpp-httplib)
+```bash
+curl -L https://raw.githubusercontent.com/yhirose/cpp-httplib/master/httplib.h -o libs/httplib.h
+```
+
+## json.hpp (nlohmann/json)
+```bash
+curl -L https://raw.githubusercontent.com/nlohmann/json/develop/single_include/nlohmann/json.hpp -o libs/json.hpp
+```
+
+## Verify
+After downloading, this directory should contain:
+```
+libs/
+├── README.md (this file)
+├── httplib.h (~800KB)
+└── json.hpp (~850KB)
+```
+
+Both are MIT licensed, single-header, no build step required.