chore: harden common storage bootstrap and slim embedded db assets

Unify embedding config, build providers from system settings, and fail
startup when index builds error or time out. Move Surreal assets under
common/db so embeds exclude crate source, and read storage via streams.

common/db/schemas/knowledge_entity_embedding.surql

@@ -0,0 +1,20 @@
+-- Defines the schema for the 'knowledge_entity_embedding' table.
+-- Separate table to optimize HNSW index creation memory usage
+
+DEFINE TABLE IF NOT EXISTS knowledge_entity_embedding SCHEMAFULL;
+
+-- Standard fields
+DEFINE FIELD IF NOT EXISTS created_at ON knowledge_entity_embedding TYPE datetime;
+DEFINE FIELD IF NOT EXISTS updated_at ON knowledge_entity_embedding TYPE datetime;
+DEFINE FIELD IF NOT EXISTS user_id ON knowledge_entity_embedding TYPE string;
+DEFINE FIELD IF NOT EXISTS source_id ON knowledge_entity_embedding TYPE string;
+
+-- Custom fields
+DEFINE FIELD IF NOT EXISTS entity_id ON knowledge_entity_embedding TYPE record<knowledge_entity>;
+DEFINE FIELD IF NOT EXISTS embedding ON knowledge_entity_embedding TYPE array<float>;
+
+-- Indexes
+-- DEFINE INDEX IF NOT EXISTS idx_embedding_knowledge_entity_embedding ON knowledge_entity_embedding FIELDS embedding HNSW DIMENSION 1536;
+DEFINE INDEX IF NOT EXISTS knowledge_entity_embedding_entity_id_idx ON knowledge_entity_embedding FIELDS entity_id UNIQUE;
+DEFINE INDEX IF NOT EXISTS knowledge_entity_embedding_user_id_idx ON knowledge_entity_embedding FIELDS user_id;
+DEFINE INDEX IF NOT EXISTS knowledge_entity_embedding_source_id_idx ON knowledge_entity_embedding FIELDS source_id;