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/text_chunk_embedding.surql

@@ -0,0 +1,20 @@
+-- Defines the schema for the 'text_chunk_embedding' table.
+-- Separate table to optimize HNSW index creation memory usage
+
+DEFINE TABLE IF NOT EXISTS text_chunk_embedding SCHEMAFULL;
+
+# Standard fields
+DEFINE FIELD IF NOT EXISTS created_at ON text_chunk_embedding TYPE datetime;
+DEFINE FIELD IF NOT EXISTS updated_at ON text_chunk_embedding TYPE datetime;
+DEFINE FIELD IF NOT EXISTS user_id ON text_chunk_embedding TYPE string;
+DEFINE FIELD IF NOT EXISTS source_id ON text_chunk_embedding TYPE string;
+
+# Custom fields
+DEFINE FIELD IF NOT EXISTS chunk_id ON text_chunk_embedding TYPE record<text_chunk>;
+DEFINE FIELD IF NOT EXISTS embedding ON text_chunk_embedding TYPE array<float>;
+
+-- Indexes
+-- DEFINE INDEX IF NOT EXISTS idx_embedding_text_chunk_embedding ON text_chunk_embedding FIELDS embedding HNSW DIMENSION 1536;
+DEFINE INDEX IF NOT EXISTS text_chunk_embedding_chunk_id_idx ON text_chunk_embedding FIELDS chunk_id UNIQUE;
+DEFINE INDEX IF NOT EXISTS text_chunk_embedding_user_id_idx ON text_chunk_embedding FIELDS user_id;
+DEFINE INDEX IF NOT EXISTS text_chunk_embedding_source_id_idx ON text_chunk_embedding FIELDS source_id;