feat(api): config + role→model routing (qwen3.5 narrator default, think off)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

api/app/config.py

@@ -0,0 +1,22 @@
+"""Server config, read from the environment at call time so tests can override
+without reimport. Charter §4 — all of this lives server-side; the client never
+sees it.
+"""
+
+import os
+
+
+def ollama_base_url() -> str:
+    return os.environ.get("OLLAMA_BASE_URL", "http://localhost:11434")
+
+
+def ollama_timeout_seconds() -> float:
+    return float(os.environ.get("OLLAMA_TIMEOUT_SECONDS", "30"))
+
+
+def narrator_model() -> str:
+    return os.environ.get("OLLAMA_NARRATOR_MODEL", "qwen3.5:latest")
+
+
+def call_log_path() -> str | None:
+    return os.environ.get("CALL_LOG_PATH") or None