fix: add missing service README.md files with basic description

services/storage-publiclink/README.md

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+# Storage PublicLink
+
+The `storage-publiclink` service provides storage backend functionality for public link shares in OpenCloud. It implements the CS3 storage provider interface specifically for managing public link shared resources.
+
+## Overview
+
+This service is part of the storage services family and is responsible for:
+- Storing metadata about public link shares
+- Providing access to publicly shared resources
+- Managing public link tokens and permissions
+- Handling anonymous access to shared content
+
+## Integration
+
+The storage-publiclink service integrates with:
+- `sharing` service - Creates and manages public link shares
+- `gateway` service - Routes requests to publicly shared resources
+- `frontend` and `ocdav` - Provide HTTP/WebDAV access to public links
+- Storage drivers - Accesses the actual file content
+
+## Storage Registry
+
+The service is registered in the gateway's storage registry with:
+- Provider ID: `7993447f-687f-490d-875c-ac95e89a62a4`
+- Mount point: `/public`
+- Space types: `grant` and `mountpoint`
+
+See the `gateway` README for more details on storage registry configuration.
+
+## Access Control
+
+Public link shares can be configured with:
+- Password protection
+- Expiration dates
+- Read-only or read-write permissions
+- Download limits
+
+## Scalability
+
+The storage-publiclink service can be scaled horizontally. When running multiple instances, ensure that the storage backend configuration is identical across all instances.