chore: initialize go-sip repository

internal/store/migrations/003_uploads.sql

@@ -0,0 +1,12 @@
+CREATE TABLE IF NOT EXISTS uploads (
+    upload_id TEXT PRIMARY KEY,
+    binding BLOB NOT NULL,
+    asset BLOB NOT NULL,
+    grant BLOB NOT NULL,
+    object_key TEXT NOT NULL,
+    state TEXT NOT NULL CHECK (state IN ('granted', 'completed', 'failed')),
+    oss_id TEXT,
+    created_at TEXT NOT NULL,
+    completed_at TEXT
+);
+CREATE INDEX IF NOT EXISTS uploads_state_idx ON uploads (state, created_at);