refactor: rename require_admin_auth/require_admin_or_agent to require_user_auth/require_user_or_agent

These dependencies check actor type (human user vs agent), not admin
privilege. The old names were misleading and could cause authorization
mistakes when wiring new endpoints. Renamed across all 10 consumer
files along with their local ADMIN_AUTH_DEP / ADMIN_OR_AGENT_DEP
aliases.

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

backend/app/api/deps.py

@@ -3,14 +3,14 @@
 These dependencies are the main "policy wiring" layer for the API.
 
 They:
-- resolve the authenticated actor (admin user vs agent)
+- resolve the authenticated actor (human user vs agent)
 - enforce organization/board access rules
 - provide common "load or 404" helpers (board/task)
 
 Why this exists:
 - Keeping authorization logic centralized makes it easier to reason about (and
   audit) permissions as the API surface grows.
-- Some routes allow either admin users or agents; others require user auth.
+- Some routes allow either human users or agents; others require user auth.
 
 If you're adding a new endpoint, prefer composing from these dependencies instead
 of re-implementing permission checks in the router.
@@ -51,7 +51,7 @@ AGENT_AUTH_OPTIONAL_DEP = Depends(get_agent_auth_context_optional)
 SESSION_DEP = Depends(get_session)
 
 
-def require_admin_auth(auth: AuthContext = AUTH_DEP) -> AuthContext:
+def require_user_auth(auth: AuthContext = AUTH_DEP) -> AuthContext:
     """Require an authenticated human user (not an agent)."""
     require_user_actor(auth)
     return auth
@@ -66,7 +66,7 @@ class ActorContext:
     agent: Agent | None = None
 
 
-def require_admin_or_agent(
+def require_user_or_agent(
     auth: AuthContext | None = AUTH_OPTIONAL_DEP,
     agent_auth: AgentAuthContext | None = AGENT_AUTH_OPTIONAL_DEP,
 ) -> ActorContext:
@@ -79,7 +79,7 @@ def require_admin_or_agent(
     raise HTTPException(status_code=status.HTTP_401_UNAUTHORIZED)
 
 
-ACTOR_DEP = Depends(require_admin_or_agent)
+ACTOR_DEP = Depends(require_user_or_agent)
 
 
 async def require_org_member(