refactor(enrichment): post tag name omits post: prefix

The inner platform:artist:id identifier remains as opaque tag.name.
Kind column carries 'post'.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/utils/metadata_enrichment.py

@@ -5,7 +5,7 @@ Metadata enrichment from Gallery-DL sidecar JSON files.
 This module handles:
 - Detection and parsing of Gallery-DL sidecar .json files
 - Extraction of metadata (dates, tags, post info) from various platforms
-- Tag generation for source tracking (source:platform, post:platform:artist:id)
+- Tag generation for source tracking (source:platform, {platform}:{artist}:{id} for post)
 - Date conflict resolution (earliest date wins)
 """
 
@@ -449,7 +449,7 @@ def generate_source_tags(metadata: dict, artist_override: Optional[str] = None)
     Returns a list of tag dictionaries with 'name' and 'kind' keys.
     Tag format ensures uniqueness:
     - source:{platform} (kind='source')
-    - post:{platform}:{artist}:{post_id} (kind='post')
+    - {platform}:{artist}:{post_id} (kind='post')
     """
     tags = []
 
@@ -469,7 +469,7 @@ def generate_source_tags(metadata: dict, artist_override: Optional[str] = None)
         # Sanitize artist name for tag (lowercase, replace spaces)
         safe_artist = artist.lower().replace(" ", "_")
         tags.append({
-            "name": f"post:{platform}:{safe_artist}:{post_id}",
+            "name": f"{platform}:{safe_artist}:{post_id}",
             "kind": "post"
         })