fix: centralize ROOT_DIR resolution, fix workspace path on Render.com, cleanup legacy paths

- Upgrade utils/storage_paths.py with robust find_repo_root() (env var override + validation + fallback)
- Remove broken _find_root() from podcast/constants.py, import from storage_paths instead
- Fix ROOT_DIR resolving to backend/ instead of project root (caused avatar upload 500s on Render.com)
- Fix video_combination_service.py default output dir (was writing to data/media instead of workspace)
- Add deprecation comments to global data/media constants in media_utils.py
- Pass user_id through resolve_media_path for tenant-scoped podcast resolution
- Add ALWRITY_ROOT_DIR env var support for explicit production overrides
- Log warning when get_podcast_media_dir called without user_id
- Use OperationButton with cost display for scene action buttons

backend/utils/media_utils.py

@@ -3,6 +3,10 @@ Media Utility Functions
 
 Centralized helper functions for loading and managing media assets across modules.
 Promotes reuse between Podcast, YouTube, and other media-heavy modules.
+
+DEPRECATED: The global DATA_MEDIA_DIR paths below are legacy and will be removed.
+New code should use workspace-scoped paths via utils.storage_paths or module-specific
+resolvers (e.g., api.podcast.constants.get_podcast_media_dir).
 """
 
 import logging
@@ -12,16 +16,19 @@ from typing import Optional, List
 from urllib.parse import urlparse
 
 from services.database import WORKSPACE_DIR
+from utils.storage_paths import get_repo_root
 
 # Configure logging
 logger = logging.getLogger(__name__)
 
-# Base Directories
-# backend/utils/media_utils.py -> parents[2] = backend/.. = root
-ROOT_DIR = Path(__file__).resolve().parents[2]
+# Base Directories — use get_repo_root() for consistent resolution
+ROOT_DIR = get_repo_root()
+
+# DEPRECATED: Global data/media paths — kept for backward-compat read fallback only.
+# New writes must go to workspace-scoped paths. Do NOT add new consumers.
 DATA_MEDIA_DIR = ROOT_DIR / "data" / "media"
 
-# Module-specific directories
+# Module-specific directories (DEPRECATED — use workspace-scoped resolvers instead)
 YOUTUBE_AVATARS_DIR = DATA_MEDIA_DIR / "youtube_avatars"
 YOUTUBE_IMAGES_DIR = DATA_MEDIA_DIR / "youtube_images"
 PODCAST_IMAGES_DIR = DATA_MEDIA_DIR / "podcast_images"
@@ -33,7 +40,7 @@ def ensure_media_dirs() -> None:
         directory.mkdir(parents=True, exist_ok=True)
 
 
-def resolve_media_path(media_url_or_path: str) -> Optional[Path]:
+def resolve_media_path(media_url_or_path: str, user_id: Optional[str] = None) -> Optional[Path]:
     """
     Resolve a media URL or filename to a concrete file path on disk.
     
@@ -41,6 +48,7 @@ def resolve_media_path(media_url_or_path: str) -> Optional[Path]:
     
     Args:
         media_url_or_path: URL path (e.g. /api/youtube/avatars/foo.png) or filename
+        user_id: Optional user ID for tenant-scoped resolution (recommended)
         
     Returns:
         Path object if found, None otherwise
@@ -70,9 +78,9 @@ def resolve_media_path(media_url_or_path: str) -> Optional[Path]:
                 parsed_path = urlparse(media_url_or_path).path
                 parts = parsed_path.split("/")
                 if len(parts) >= 6:
-                    user_id = parts[3]
-                    safe_user_id = "".join(c for c in user_id if c.isalnum() or c in ("-", "_"))
-                    if safe_user_id == user_id:
+                    asset_user_id = parts[3]
+                    safe_user_id = "".join(c for c in asset_user_id if c.isalnum() or c in ("-", "_"))
+                    if safe_user_id == asset_user_id:
                         safe_filename = os.path.basename(filename)
                         assets_path = Path(WORKSPACE_DIR) / f"workspace_{safe_user_id}" / "assets" / "avatars" / safe_filename
                         if assets_path.exists() and assets_path.is_file():
@@ -82,7 +90,7 @@ def resolve_media_path(media_url_or_path: str) -> Optional[Path]:
                 logger.error(f"[MediaUtils] Error resolving assets avatar path: {exc}")
 
         # Define search paths in order of likelihood
-        # We search all avatar/image directories
+        # We search all avatar/image directories (DEPRECATED: global paths — kept for backward-compat reads)
         search_paths: List[Path] = [
             YOUTUBE_AVATARS_DIR / filename,
             PODCAST_AVATARS_DIR / filename,
@@ -101,7 +109,7 @@ def resolve_media_path(media_url_or_path: str) -> Optional[Path]:
             try:
                 # Import the centralized function that checks tenant workspace first
                 from api.podcast.constants import get_podcast_media_read_dirs
-                podcast_dirs = get_podcast_media_read_dirs("image")
+                podcast_dirs = get_podcast_media_read_dirs("image", user_id=user_id)
                 search_paths = []
                 for pod_dir in podcast_dirs:
                     # Add both avatar and image subdirectories

backend/utils/storage_paths.py

@@ -1,8 +1,11 @@
 from __future__ import annotations
 
+import os
 from pathlib import Path
 from typing import Iterable
 
+from loguru import logger
+
 _SAFE_CHARS = {"-", "_"}
 
 
@@ -16,9 +19,46 @@ def _sanitize_segment(value: str, fallback: str) -> str:
     return cleaned or fallback
 
 
+def find_repo_root() -> Path:
+    """Find the project repository root directory.
+
+    Resolution order:
+    1. ALWRITY_ROOT_DIR environment variable (explicit override for production)
+    2. Deterministic path from this file (storage_paths.py is at utils/)
+    3. Walk-up fallback looking for a 'backend/' directory at project root
+
+    Returns an absolute, resolved Path.
+    """
+    env_root = os.environ.get("ALWRITY_ROOT_DIR")
+    if env_root:
+        root = Path(env_root).resolve()
+        if root.is_dir():
+            return root
+
+    # storage_paths.py is at backend/utils/storage_paths.py
+    # project root is parents[2] (utils -> backend -> root)
+    this_file = Path(__file__).resolve()
+    candidate = this_file.parents[2]
+
+    if (candidate / "backend").is_dir():
+        return candidate
+
+    # Walk-up fallback for unusual deployments
+    current = this_file.parent
+    for _ in range(10):
+        if (current / "backend").is_dir():
+            return current
+        parent = current.parent
+        if parent == current:
+            break
+        current = parent
+
+    return this_file.parents[2]
+
+
 def get_repo_root() -> Path:
     """Return repository root as an absolute canonical path."""
-    return Path(__file__).resolve().parents[2]
+    return find_repo_root()
 
 
 def get_workspace_root() -> Path:
@@ -67,3 +107,7 @@ def get_legacy_video_studio_upload_dirs() -> list[Path]:
         (repo_root / "backend" / "data" / "video_studio" / "uploads").resolve(),
         (repo_root / "backend" / "backend" / "data" / "video_studio" / "uploads").resolve(),
     ]
+
+
+# Log resolved root at import time for production debugging
+logger.info(f"[StoragePaths] Repository root resolved to: {get_repo_root()}")