Database basic CRUD (#27)

* started schema

* db schemas beginning

* first db schema gen

* added sqlc generation with go generate and sqlite driver

* i think these dependencies are needed

* added IF NOT EXISTS to create and CRUD for each table

* fixed missing columns

* added missing field

* fixed code generation with sqlc

backend/database/sql/schemas/audio_files.sql

@@ -0,0 +1,9 @@
+CREATE TABLE IF NOT EXISTS audio_files (
+  id int PRIMARY KEY,
+  file_path text NOT NULL UNIQUE,
+  length_milliseconds int NOT NULL,
+  file_type_id int NOT NULL,
+  recording_id int NOT NULL,
+  FOREIGN KEY(file_type_id) REFERENCES file_types(id),
+  FOREIGN KEY(recording_id) REFERENCES recordings(id)
+);