refactor(pipelines): address code review - shared get_current_user_id, aria-live, deduplicate user ID logic

- Extract _get_user_id into shared auth.get_current_user_id() used by both
  pipelines API and the assign-pipeline endpoint in files API
- Fix aria-live attribute: use two separate static containers (polite/assertive)
  instead of dynamic Alpine.js binding for correct screen reader announcements
- Fix migration comment to accurately describe batch-mode FK creation
- Remove redundant tags parameter from reorder endpoint decorator
- Rename _make_file test helper to _make_test_file_record for clarity
- Update docs/UserGuide.md and docs/API.md with full Pipelines reference

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

app/api/files.py

@@ -1590,15 +1590,11 @@ def assign_pipeline_to_file(
         HTTPException 404: If the file or pipeline does not exist / is not
             accessible to the current user.
     """
-    from app.auth import get_current_user
+    from app.auth import get_current_user, get_current_user_id
     from app.models import Pipeline
 
     user = get_current_user(request)
-    # Derive user identity the same way the pipelines API does (_get_user_id)
-    if user:
-        user_id: str = user.get("preferred_username") or user.get("email") or user.get("id") or "anonymous"
-    else:
-        user_id = "anonymous"
+    user_id: str = get_current_user_id(request)
 
     is_admin_user = bool(user and user.get("is_admin"))
 

app/api/pipelines.py

@@ -18,7 +18,7 @@ from fastapi import APIRouter, Body, Depends, HTTPException, Request, status
 from pydantic import BaseModel, Field
 from sqlalchemy.orm import Session
 
-from app.auth import get_current_user, require_login
+from app.auth import get_current_user, get_current_user_id, require_login
 from app.database import get_db
 from app.models import Pipeline, PipelineStep
 
@@ -90,11 +90,12 @@ MAX_NAME_LENGTH = 255
 
 
 def _get_user_id(request: Request) -> str:
-    """Return a stable user identifier from the session."""
-    user = get_current_user(request)
-    if user:
-        return user.get("preferred_username") or user.get("email") or user.get("id", "anonymous")
-    return "anonymous"
+    """Return a stable user identifier from the session.
+
+    Delegates to :func:`app.auth.get_current_user_id` so the same fallback
+    logic ("anonymous") is used consistently throughout the application.
+    """
+    return get_current_user_id(request)
 
 
 def _is_admin(request: Request) -> bool:
@@ -591,7 +592,7 @@ def add_step(pipeline_id: int, request: Request, db: DbSession, body: PipelineSt
     return _serialize_step(step)
 
 
-@router.put("/{pipeline_id}/steps/reorder", tags=["pipelines"])
+@router.put("/{pipeline_id}/steps/reorder")
 @require_login
 def reorder_steps(
     pipeline_id: int,