refactor(constants): single source of truth for data dir (#3368)

* refactor(constants): single source of truth for data dir + merge core/src constants

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* docs(contributing): use named src.constants for data paths, drop core/constants references

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

setup.py

@@ -12,19 +12,24 @@ import subprocess
 import sys
 
 BASE_DIR = os.path.dirname(os.path.abspath(__file__))
-DATA_DIR = os.path.join(BASE_DIR, "data")
+sys.path.insert(0, BASE_DIR)
+from src.constants import (
+    DATA_DIR, AUTH_FILE, UPLOAD_DIR, PERSONAL_DIR, PERSONAL_UPLOADS_DIR,
+    TTS_CACHE_DIR, GENERATED_IMAGES_DIR, DEEP_RESEARCH_DIR, CHROMA_DIR,
+    RAG_DIR, MEMORY_VECTORS_DIR,
+)
 
 DIRS = [
     DATA_DIR,
-    os.path.join(DATA_DIR, "uploads"),
-    os.path.join(DATA_DIR, "personal_docs"),
-    os.path.join(DATA_DIR, "personal_uploads"),
-    os.path.join(DATA_DIR, "tts_cache"),
-    os.path.join(DATA_DIR, "generated_images"),
-    os.path.join(DATA_DIR, "deep_research"),
-    os.path.join(DATA_DIR, "chroma"),
-    os.path.join(DATA_DIR, "rag"),
-    os.path.join(DATA_DIR, "memory_vectors"),
+    UPLOAD_DIR,
+    PERSONAL_DIR,
+    PERSONAL_UPLOADS_DIR,
+    TTS_CACHE_DIR,
+    GENERATED_IMAGES_DIR,
+    DEEP_RESEARCH_DIR,
+    CHROMA_DIR,
+    RAG_DIR,
+    MEMORY_VECTORS_DIR,
     os.path.join(BASE_DIR, "logs"),
 ]
 
@@ -74,7 +79,7 @@ def _prompt_admin_credentials():
 
 def create_default_admin():
     """Create an initial admin user if none exists."""
-    auth_path = os.path.join(DATA_DIR, "auth.json")
+    auth_path = AUTH_FILE
     if os.path.exists(auth_path):
         print("  [skip] auth.json already exists")
         return "exists"