feat: add database storage backend (#1091)

Co-authored-by: Elias Schneider <login@eliasschneider.com>

backend/resources/migrations/postgres/20251110000000_storage_table.up.sql

@@ -0,0 +1,9 @@
+-- The "storage" table contains file data stored in the database
+CREATE TABLE storage
+(
+    path       TEXT NOT NULL PRIMARY KEY,
+    data       BYTEA NOT NULL,
+    size       BIGINT NOT NULL,
+    mod_time   TIMESTAMPTZ NOT NULL,
+    created_at TIMESTAMPTZ NOT NULL
+);