proto: add vector_dimension option and SimilaritySearch RPC

proto/database.proto

@@ -43,6 +43,7 @@ service DatabaseService {
     // Query operations
     rpc Find(FindRequest) returns (FindResponse);
     rpc Count(CountRequest) returns (CountResponse);
+    rpc SimilaritySearch(SimilaritySearchRequest) returns (SimilaritySearchResponse);
 
     // Set operations (Redis compatibility)
     rpc SetAdd(SetAddRequest) returns (SetAddResponse);
@@ -332,6 +333,23 @@ message CountResponse {
     uint64 count = 1;
 }
 
+message SimilaritySearchRequest {
+    string collection = 1;
+    repeated float query_vector = 2;
+    uint32 top_k = 3;
+    float min_score = 4;
+}
+
+message SimilaritySearchResponse {
+    repeated SimilarityResult results = 1;
+}
+
+message SimilarityResult {
+    string id = 1;
+    float score = 2;
+    bytes data = 3;
+}
+
 // ===== Set Operations =====
 
 message SetAddRequest {
@@ -386,6 +404,7 @@ message CollectionOptions {
     bool encrypted = 3;
     repeated string sensitive_fields = 4;
     uint32 max_versions = 5;          // Max version history per document (0 = unlimited)
+    uint32 vector_dimension = 6;      // Dimension of vectors stored in this collection (0 = not a vector collection)
 }
 
 message CreateCollectionResponse {
@@ -423,6 +442,7 @@ message CollectionInfo {
     CollectionOptions options = 4;
     uint64 created_at = 5;
     uint64 updated_at = 6;
+    uint32 vector_dimension = 7;      // Dimension of vectors stored in this collection (0 = not a vector collection)
 }
 
 // ===== File Operations =====