Consolidate database schema into two files: init migrations table and complete schema

Since there is no existing installed base, we can consolidate all migrations into a single complete schema file plus the migrations table initialization. This simplifies the database setup for new installations.

internal/database/migrations/001_init_migrations.sql

@@ -0,0 +1,6 @@
+-- Initialize migrations table for tracking applied migrations
+CREATE TABLE IF NOT EXISTS migrations (
+    id INTEGER PRIMARY KEY,
+    name TEXT NOT NULL UNIQUE,
+    applied_at DATETIME DEFAULT CURRENT_TIMESTAMP
+);