fix: Use HF Spaces persistent /data storage for uploaded files

Uploaded documents were lost on every Space rebuild because /app/uploads
is ephemeral. Now the config detects if /data is writable (HF Spaces
persistent storage) and stores uploads, outputs, ChromaDB, and templates
there instead. Files survive container rebuilds.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Dockerfile

@@ -45,8 +45,9 @@ COPY --chown=user backend/ .
 COPY --chown=user --from=frontend_builder /app/out /app/static
 
 # Create directory structure and set permissions
-RUN mkdir -p /app/uploads /app/outputs /app/chroma_db /app/templates && \
-    chmod -R 777 /app/uploads /app/outputs /app/chroma_db
+# /app/* is ephemeral fallback; /data/* is HF Spaces persistent storage
+RUN mkdir -p /app/uploads /app/outputs /app/chroma_db /app/templates /data && \
+    chmod -R 777 /app/uploads /app/outputs /app/chroma_db /data
 
 # Switch to non-root user
 USER user

backend/app/core/config.py

@@ -49,7 +49,7 @@ class Settings(BaseSettings):
     CHUNK_SIZE: int = 512
     CHUNK_OVERLAP: int = 50
 
-    # Storage paths
+    # Storage paths (defaults; overridden below for HF Spaces persistent storage)
     UPLOAD_DIR: str = "./uploads"
     OUTPUT_DIR: str = "./outputs"
     TEMPLATE_DIR: str = "./templates"
@@ -61,6 +61,16 @@ class Settings(BaseSettings):
 
 settings = Settings()
 
+# On HF Spaces, use /data for persistent storage so files survive rebuilds.
+# The /data volume is available when "Persistent storage" is enabled in Space settings.
+_persistent_root = "/data"
+if os.path.isdir(_persistent_root) and os.access(_persistent_root, os.W_OK):
+    settings.UPLOAD_DIR = os.path.join(_persistent_root, "uploads")
+    settings.OUTPUT_DIR = os.path.join(_persistent_root, "outputs")
+    settings.TEMPLATE_DIR = os.path.join(_persistent_root, "templates")
+    settings.CHROMA_PERSIST_DIR = os.path.join(_persistent_root, "chroma_db")
+    settings.COMPETITOR_DB_PATH = os.path.join(_persistent_root, "competitors.json")
+
 # Ensure directories exist
 for dir_path in [settings.UPLOAD_DIR, settings.OUTPUT_DIR, settings.TEMPLATE_DIR, settings.CHROMA_PERSIST_DIR, "./data"]:
     os.makedirs(dir_path, exist_ok=True)