chore(schema): migrate to GORM V2 with multi-database support

- [x] Implement GORM V2 metadata store with SQLite, PostgreSQL, and MySQL support
- [x] Add database migration system using gormigrate for schema versioning
- [x] Create migration CLI tool with support for migrate, rollback, and status commands
- [x] Add Docker support for migration container (Dockerfile.migrate)
- [x] Implement automatic partition management for PostgreSQL time-series tables
- [x] Add background aggregation worker for download statistics
- [x] Support connection pooling configuration (max_open_conns, max_idle_conns, conn_max_lifetime)
- [x] Add blocking mechanism based on vulnerability thresholds in stats and handlers
- [x] Update Helm charts with migration init containers and multi-database configuration
- [x] Replace deprecated SQLite store with optimized GORM implementation
- [x] Add comprehensive integration tests for MySQL and PostgreSQL
- [x] Update frontend to display blocked packages and storage utilization
- [x] Add goreleaser configuration for migrate binary and container image
- [x] Update configuration examples with database backend options and recommendations

Dockerfile.migrate

@@ -0,0 +1,30 @@
+# Migration Engine - Database Migration Tool
+ARG TARGETOS
+ARG TARGETARCH
+
+FROM alpine:latest
+
+# Install runtime dependencies
+RUN apk add --no-cache \
+    ca-certificates \
+    postgresql-client \
+    mysql-client \
+    busybox-extras \
+    && update-ca-certificates
+
+# Create non-root user
+RUN addgroup -g 1000 gohoarder && \
+    adduser -D -u 1000 -G gohoarder gohoarder
+
+# Copy binary (from platform-specific path)
+ARG TARGETOS
+ARG TARGETARCH
+COPY ${TARGETOS}/${TARGETARCH}/migrate /usr/local/bin/migrate
+RUN chmod +x /usr/local/bin/migrate
+
+WORKDIR /app
+USER gohoarder
+
+# Run migrations
+ENTRYPOINT ["/usr/local/bin/migrate"]
+CMD ["--action=migrate"]