feat: add OrcaRouter embedder for hosted semantic search

Add a named OrcaRouterEmbedder mirroring the existing OpenRouterEmbedder:
a production AI gateway that proxies 200+ models on one OpenAI-compatible
endpoint (https://api.orcarouter.ai/v1). Selecting it is a one-line switch:
set ORCAROUTER_API_KEY instead of OPENROUTER_API_KEY.

- get_embedder() prefers OrcaRouter when ORCAROUTER_API_KEY is present
- is_semantic_search_available() now also enables on OrcaRouter keys
- document the new option in README (Alternatif 3) and .env.example

Co-Authored-By: Claude <noreply@anthropic.com>
Signed-off-by: jinhao.song <jinhao.song@myflashcloud.com>

semantic_search/__init__.py

@@ -2,9 +2,11 @@
 
 from .embedder import (
     OpenRouterEmbedder,
+    OrcaRouterEmbedder,
     LocalEmbedder,
     get_embedder,
     is_openrouter_available,
+    is_orcarouter_available,
     is_local_embedding_configured,
     is_semantic_search_available,
 )
@@ -13,9 +15,11 @@ from .processor import DocumentProcessor
 
 __all__ = [
     'OpenRouterEmbedder',
+    'OrcaRouterEmbedder',
     'LocalEmbedder',
     'get_embedder',
     'is_openrouter_available',
+    'is_orcarouter_available',
     'is_local_embedding_configured',
     'is_semantic_search_available',
     'VectorStore',