Restructure inference docs (#2225)

* Break Inference page into several pages

* Make all inference code snippets testable and clean up

* Make more snippets testable

* Edits

* Document automatic query and passage prefix injection in Cloud Inference

Qdrant Cloud Inference silently applies model-specific prefixes (e.g.
"query: "/"passage: " for E5, BGE-style instruction prefix for BGE/mxbai/
Snowflake arctic-embed) so users don't need to manage them manually.
Add a section explaining this behavior, the idempotency guarantee, and
the scope (Qdrant-hosted models only; external providers handle their own).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Document short query optimization in Cloud Inference

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* Update links

* Expand on external provider API key usage

* Add section about external provider API keys

* Default to header for external API keys

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

qdrant-landing/content/documentation/headless/snippets/inference/jinaai-upsert/go.go

@@ -7,16 +7,20 @@ import (
 )
 
 func Main() {
+	// @hide-start
 	client, err := qdrant.NewClient(&qdrant.Config{
 		Host:   "xyz-example.qdrant.io",
 		Port:   6334,
 		APIKey: "<paste-your-api-key-here>",
 		UseTLS: true,
 	})
+	// @hide-end
 
 	if err != nil { panic(err) } // @hide
 
-	client.Upsert(context.Background(), &qdrant.UpsertPoints{
+	ctx := qdrant.WithHeader(context.Background(), "jina-api-key", "<YOUR_JINAAI_API_KEY>")
+
+	client.Upsert(ctx, &qdrant.UpsertPoints{
 		CollectionName: "{collection_name}",
 		Points: []*qdrant.PointStruct{
 			{
@@ -25,8 +29,7 @@ func Main() {
 					Model: "jinaai/jina-clip-v2",
 					Image: qdrant.NewValueString("https://qdrant.tech/example.png"),
 					Options: qdrant.NewValueMap(map[string]any{
-						"jina-api-key": "<YOUR_JINAAI_API_KEY>",
-						"dimensions":   512,
+						"dimensions": 512,
 					}),
 				}),
 			},