Add Streamlit web interface (app.py)

Eight-screen workflow: start → research → sources → storyline → draft →
quality → publication → history. 2×2 provider grid for storyline and
draft comparison. Inline text editing plus AI revision at draft and
quality steps. Download and copy-to-clipboard for publication package.
Session resume on startup.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pyproject.toml

@@ -4,6 +4,7 @@ version = "0.1.0"
 requires-python = ">=3.11"
 dependencies = [
     "anthropic>=0.49.0",
+    "streamlit>=1.35.0",
     "openai>=1.0.0",
     "google-genai>=1.0.0",
     "mistralai>=1.0.0",