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.surql

@@ -0,0 +1,17 @@
+# Defines the schema for the 'text_chunk' table.
+
+DEFINE TABLE IF NOT EXISTS text_chunk SCHEMALESS;
+
+# Standard fields
+DEFINE FIELD IF NOT EXISTS created_at ON text_chunk TYPE datetime;
+DEFINE FIELD IF NOT EXISTS updated_at ON text_chunk TYPE datetime;
+
+# Custom fields from the TextChunk struct
+DEFINE FIELD IF NOT EXISTS source_id ON text_chunk TYPE string;
+DEFINE FIELD IF NOT EXISTS chunk ON text_chunk TYPE string;
+
+DEFINE FIELD IF NOT EXISTS user_id ON text_chunk TYPE string;
+
+# Indexes based on build_indexes and query patterns (delete_by_source_id)
+DEFINE INDEX IF NOT EXISTS text_chunk_source_id_idx ON text_chunk FIELDS source_id;
+DEFINE INDEX IF NOT EXISTS text_chunk_user_id_idx ON text_chunk FIELDS user_id;