feat: add souls directory integration with search and fetch functionality

backend/app/schemas/souls_directory.py

@@ -0,0 +1,21 @@
+from __future__ import annotations
+
+from pydantic import BaseModel
+
+
+class SoulsDirectorySoulRef(BaseModel):
+    handle: str
+    slug: str
+    page_url: str
+    raw_md_url: str
+
+
+class SoulsDirectorySearchResponse(BaseModel):
+    items: list[SoulsDirectorySoulRef]
+
+
+class SoulsDirectoryMarkdownResponse(BaseModel):
+    handle: str
+    slug: str
+    content: str
+