Remove tag system, use versions only for artifact references

Tags were mutable aliases that caused confusion alongside the immutable
version system. This removes tags entirely, keeping only PackageVersion
for artifact references.

Changes:
- Remove tags and tag_history tables (migration 012)
- Remove Tag model, TagRepository, and 6 tag API endpoints
- Update cache system to create versions instead of tags
- Update frontend to display versions instead of tags
- Remove tag-related schemas and types
- Update artifact cleanup service for version-based ref_count

backend/app/seed.py

@@ -5,7 +5,7 @@ import hashlib
 import logging
 from sqlalchemy.orm import Session
 
-from .models import Project, Package, Artifact, Tag, Upload, PackageVersion, ArtifactDependency, Team, TeamMembership, User
+from .models import Project, Package, Artifact, Upload, PackageVersion, ArtifactDependency, Team, TeamMembership, User
 from .storage import get_storage
 from .auth import hash_password
 
@@ -125,14 +125,14 @@ TEST_ARTIFACTS = [
 ]
 
 # Dependencies to create (source artifact -> dependency)
-# Format: (source_project, source_package, source_version, dep_project, dep_package, version_constraint, tag_constraint)
+# Format: (source_project, source_package, source_version, dep_project, dep_package, version_constraint)
 TEST_DEPENDENCIES = [
     # ui-components v1.1.0 depends on design-tokens v1.0.0
-    ("frontend-libs", "ui-components", "1.1.0", "frontend-libs", "design-tokens", "1.0.0", None),
+    ("frontend-libs", "ui-components", "1.1.0", "frontend-libs", "design-tokens", "1.0.0"),
     # auth-lib v1.0.0 depends on common-utils v2.0.0
-    ("backend-services", "auth-lib", "1.0.0", "backend-services", "common-utils", "2.0.0", None),
-    # auth-lib v1.0.0 also depends on design-tokens (stable tag)
-    ("backend-services", "auth-lib", "1.0.0", "frontend-libs", "design-tokens", None, "latest"),
+    ("backend-services", "auth-lib", "1.0.0", "backend-services", "common-utils", "2.0.0"),
+    # auth-lib v1.0.0 also depends on design-tokens v1.0.0
+    ("backend-services", "auth-lib", "1.0.0", "frontend-libs", "design-tokens", "1.0.0"),
 ]
 
 
@@ -252,9 +252,8 @@ def seed_database(db: Session) -> None:
 
     logger.info(f"Created {len(project_map)} projects and {len(package_map)} packages (assigned to {demo_team.slug})")
 
-    # Create artifacts, tags, and versions
+    # Create artifacts and versions
     artifact_count = 0
-    tag_count = 0
     version_count = 0
 
     for artifact_data in TEST_ARTIFACTS:
@@ -316,23 +315,12 @@ def seed_database(db: Session) -> None:
             db.add(version)
             version_count += 1
 
-        # Create tags
-        for tag_name in artifact_data["tags"]:
-            tag = Tag(
-                package_id=package.id,
-                name=tag_name,
-                artifact_id=sha256_hash,
-                created_by=team_owner_username,
-            )
-            db.add(tag)
-            tag_count += 1
-
     db.flush()
 
     # Create dependencies
     dependency_count = 0
     for dep_data in TEST_DEPENDENCIES:
-        src_project, src_package, src_version, dep_project, dep_package, version_constraint, tag_constraint = dep_data
+        src_project, src_package, src_version, dep_project, dep_package, version_constraint = dep_data
 
         # Find the source artifact by looking up its version
         src_pkg = package_map.get((src_project, src_package))
@@ -356,11 +344,10 @@ def seed_database(db: Session) -> None:
             dependency_project=dep_project,
             dependency_package=dep_package,
             version_constraint=version_constraint,
-            tag_constraint=tag_constraint,
         )
         db.add(dependency)
         dependency_count += 1
 
     db.commit()
-    logger.info(f"Created {artifact_count} artifacts, {tag_count} tags, {version_count} versions, and {dependency_count} dependencies")
+    logger.info(f"Created {artifact_count} artifacts, {version_count} versions, and {dependency_count} dependencies")
     logger.info("Database seeding complete")