Refactor backend to SQLModel; reset schema; add Company OS endpoints

backend/app/schemas/projects.py

@@ -0,0 +1,13 @@
+from __future__ import annotations
+
+from sqlmodel import SQLModel
+
+
+class ProjectCreate(SQLModel):
+    name: str
+    status: str = "active"
+
+
+class ProjectUpdate(SQLModel):
+    name: str | None = None
+    status: str | None = None