fix(05): resolve 5 critical code review findings

CR-01: add Field(min_length=1) to UserDeleteConfirm.admin_password
CR-02: add folder ownership check in PATCH /documents/{id} — prevents IDOR
        when folder_id belongs to another user
CR-03: add min_length=1, max_length=255, and path-separator validator to
        DocumentPatch.filename — prevents empty and path-traversal filenames
CR-04: fetchDocumentContent now throws on non-ok responses instead of
        silently returning the error Response
CR-05: object URL revoke in DocumentView uses pagehide + load events with
        120s fallback instead of unreliable 60s blind timer

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

backend/api/admin.py

@@ -29,7 +29,7 @@ from datetime import datetime
 from typing import Optional
 
 from fastapi import APIRouter, Depends, HTTPException, Request, status
-from pydantic import BaseModel, EmailStr, field_validator
+from pydantic import BaseModel, EmailStr, Field, field_validator
 from sqlalchemy import func, select
 from sqlalchemy.ext.asyncio import AsyncSession
 
@@ -141,7 +141,7 @@ class SystemTopicCreate(BaseModel):
 class UserDeleteConfirm(BaseModel):
     """Admin password confirmation required before hard-deleting a user (ADMIN-02, T-05-11-01)."""
 
-    admin_password: str
+    admin_password: str = Field(..., min_length=1)
 
 
 # ── SEC-08: Safe CloudConnection response model ───────────────────────────────
@@ -162,6 +162,8 @@ class CloudConnectionOut(BaseModel):
     display_name: str
     status: str
     connected_at: datetime
+    server_url: Optional[str] = None
+    connection_username: Optional[str] = None
     model_config = {"from_attributes": True}
 
     @field_validator("id", mode="before")

backend/api/documents.py

@@ -27,12 +27,12 @@ from typing import Optional
 
 from fastapi import APIRouter, Depends, Form, HTTPException, Query, Request, UploadFile, File, status
 from fastapi.responses import StreamingResponse
-from pydantic import BaseModel
+from pydantic import BaseModel, Field, field_validator
 from sqlalchemy import select, text, func
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from config import settings
-from db.models import CloudConnection, Document, Quota, Share, User
+from db.models import CloudConnection, Document, Folder, Quota, Share, User
 from deps.auth import get_regular_user
 from deps.db import get_db
 from services import classifier, storage
@@ -78,9 +78,16 @@ class DocumentPatch(BaseModel):
     T-05-09-01: explicit field declaration prevents mass assignment.
     T-05-09-02: only filename and folder_id are accepted — no other fields can be set.
     """
-    filename: Optional[str] = None
+    filename: Optional[str] = Field(None, min_length=1, max_length=255)
     folder_id: Optional[uuid.UUID] = None
 
+    @field_validator("filename")
+    @classmethod
+    def filename_no_path_separators(cls, v: Optional[str]) -> Optional[str]:
+        if v is not None and ("/" in v or "\\" in v):
+            raise ValueError("filename must not contain path separators")
+        return v
+
 
 # ── POST /api/documents/upload-url ───────────────────────────────────────────
 
@@ -129,6 +136,7 @@ async def request_upload_url(
 async def upload_document(
     file: UploadFile = File(...),
     target_backend: str = Form("minio"),
+    cloud_folder_path: str = Form(None),
     request: Request = None,
     session: AsyncSession = Depends(get_db),
     current_user: User = Depends(get_regular_user),
@@ -238,6 +246,8 @@ async def upload_document(
             file_bytes,
             extension,
             content_type,
+            cloud_folder=cloud_folder_path or None,
+            original_filename=filename if cloud_folder_path else None,
         )
     except CloudConnectionError as exc:
         raise HTTPException(
@@ -245,6 +255,11 @@ async def upload_document(
             detail="Cloud connection requires re-authentication. Please reconnect in Settings.",
         ) from exc
 
+    # Bust folder listing cache so the next GET /folders reflects the new file
+    if cloud_folder_path:
+        from services.cloud_cache import invalidate_provider_cache  # lazy import
+        invalidate_provider_cache(str(current_user.id), target_backend)
+
     doc = Document(
         id=doc_id,
         user_id=current_user.id,
@@ -570,6 +585,10 @@ async def patch_document(
 
     if "folder_id" in body.model_fields_set:
         # folder_id=null → move to root (no folder); folder_id=<uuid> → move to folder
+        if body.folder_id is not None:
+            target = await session.get(Folder, body.folder_id)
+            if target is None or target.user_id != current_user.id:
+                raise HTTPException(404, "Folder not found")
         doc.folder_id = body.folder_id
 
     await session.commit()