drop multi-node ssh execution, unify job runner to local + fix job completion atomicity

- remove nodes table, ssh service, nodes api, NodesPage route
- execute.ts: local-only spawn, atomic CAS job claim via UPDATE status
- wrap job done + subtitle_files insert + review_plans status in db transaction
- stream ffmpeg output per line with 500ms throttled flush
- bump version to 2026.04.13

server/db/schema.ts

@@ -7,22 +7,6 @@ CREATE TABLE IF NOT EXISTS config (
 	value TEXT
 );
 
-CREATE TABLE IF NOT EXISTS nodes (
-	id              INTEGER PRIMARY KEY AUTOINCREMENT,
-	name            TEXT NOT NULL UNIQUE,
-	host            TEXT NOT NULL,
-	port            INTEGER NOT NULL DEFAULT 22,
-	username        TEXT NOT NULL,
-	private_key     TEXT NOT NULL,
-	ffmpeg_path     TEXT NOT NULL DEFAULT 'ffmpeg',
-	work_dir        TEXT NOT NULL DEFAULT '/tmp',
-	movies_path     TEXT NOT NULL DEFAULT '',
-	series_path     TEXT NOT NULL DEFAULT '',
-	status          TEXT NOT NULL DEFAULT 'unknown',
-	last_checked_at TEXT,
-	created_at      TEXT NOT NULL DEFAULT (datetime('now'))
-);
-
 CREATE TABLE IF NOT EXISTS media_items (
 	id                   INTEGER PRIMARY KEY AUTOINCREMENT,
 	jellyfin_id          TEXT NOT NULL UNIQUE,
@@ -104,7 +88,6 @@ CREATE TABLE IF NOT EXISTS jobs (
 	item_id      INTEGER NOT NULL REFERENCES media_items(id) ON DELETE CASCADE,
 	command      TEXT NOT NULL,
 	job_type     TEXT NOT NULL DEFAULT 'audio',
-	node_id      INTEGER REFERENCES nodes(id) ON DELETE SET NULL,
 	status       TEXT NOT NULL DEFAULT 'pending',
 	output       TEXT,
 	exit_code    INTEGER,