Add separate version tracking for artifacts

- Add package_versions table with immutable version records
- Support version detection from explicit param, metadata, or filename
- Add version API endpoints (list, get, delete)
- Update ref resolution to check versions before tags
- Add version column to tags table in frontend UI
- Add Create Tag form for pointing tags at existing artifacts
- Update seed data with version records
- Add 16 integration tests for version functionality

frontend/src/pages/PackagePage.css

@@ -324,6 +324,86 @@ tr:hover .copy-btn {
   color: var(--text-muted);
 }
 
+/* Version badge */
+.version-badge {
+  font-family: 'JetBrains Mono', 'Fira Code', 'Consolas', monospace;
+  font-size: 0.8125rem;
+  color: var(--accent-primary);
+  background: rgba(16, 185, 129, 0.1);
+  padding: 2px 8px;
+  border-radius: var(--radius-sm);
+}
+
+/* Create Tag Section */
+.create-tag-section {
+  margin-top: 32px;
+  background: var(--bg-secondary);
+}
+
+.create-tag-section h3 {
+  margin-bottom: 4px;
+  color: var(--text-primary);
+  font-size: 1rem;
+  font-weight: 600;
+}
+
+.section-description {
+  color: var(--text-muted);
+  font-size: 0.875rem;
+  margin-bottom: 16px;
+}
+
+.create-tag-form .form-row {
+  display: flex;
+  gap: 12px;
+  align-items: flex-end;
+  flex-wrap: wrap;
+}
+
+.create-tag-form .form-group {
+  flex: 1;
+  min-width: 150px;
+}
+
+.create-tag-form .form-group--wide {
+  flex: 2;
+  min-width: 300px;
+}
+
+.create-tag-form .form-group label {
+  display: block;
+  margin-bottom: 6px;
+  font-size: 0.75rem;
+  font-weight: 500;
+  color: var(--text-secondary);
+  text-transform: uppercase;
+  letter-spacing: 0.05em;
+}
+
+.create-tag-form .form-group input {
+  width: 100%;
+  padding: 10px 14px;
+  background: var(--bg-tertiary);
+  border: 1px solid var(--border-primary);
+  border-radius: var(--radius-md);
+  color: var(--text-primary);
+  font-size: 0.875rem;
+}
+
+.create-tag-form .form-group input:focus {
+  outline: none;
+  border-color: var(--accent-primary);
+}
+
+.create-tag-form .form-group input:disabled {
+  opacity: 0.6;
+  cursor: not-allowed;
+}
+
+.create-tag-form button {
+  flex-shrink: 0;
+}
+
 /* Created cell */
 .created-cell {
   display: flex;