refactor: Modularize server into separate concerns

Split monolithic index.ts (~1400 lines) into modular structure:
- config.ts: Server configuration and constants
- db/: Database initialization, migrations, and seeds
- routes/: API handlers by domain (themes, canvas, components, etc.)
- services/: Terminal WebSocket server
- utils/: CORS helpers

Entry point now only coordinates initialization.

server/db/migrations.ts

@@ -0,0 +1,107 @@
+import type { Database } from 'bun:sqlite'
+
+export function runMigrations(db: Database) {
+  // History table
+  db.run(`
+    CREATE TABLE IF NOT EXISTS history (
+      id INTEGER PRIMARY KEY AUTOINCREMENT,
+      timestamp TEXT DEFAULT CURRENT_TIMESTAMP,
+      tool_name TEXT NOT NULL,
+      args TEXT,
+      result TEXT
+    )
+  `)
+
+  // Config table
+  db.run(`
+    CREATE TABLE IF NOT EXISTS config (
+      key TEXT PRIMARY KEY,
+      value TEXT
+    )
+  `)
+
+  // Vue components table
+  db.run(`
+    CREATE TABLE IF NOT EXISTS vue_components (
+      id TEXT PRIMARY KEY,
+      name TEXT NOT NULL,
+      template TEXT NOT NULL,
+      setup TEXT,
+      style TEXT,
+      props TEXT,
+      imports TEXT,
+      created_at TEXT DEFAULT CURRENT_TIMESTAMP,
+      updated_at TEXT DEFAULT CURRENT_TIMESTAMP
+    )
+  `)
+
+  // Themes table
+  db.run(`
+    CREATE TABLE IF NOT EXISTS themes (
+      id TEXT PRIMARY KEY,
+      name TEXT NOT NULL,
+      description TEXT,
+      is_default INTEGER DEFAULT 0,
+      is_system INTEGER DEFAULT 0,
+      variables TEXT NOT NULL,
+      metadata TEXT,
+      created_at TEXT DEFAULT CURRENT_TIMESTAMP,
+      updated_at TEXT DEFAULT CURRENT_TIMESTAMP
+    )
+  `)
+
+  // Project canvas table
+  db.run(`
+    CREATE TABLE IF NOT EXISTS project_canvas (
+      id TEXT PRIMARY KEY,
+      name TEXT NOT NULL,
+      description TEXT,
+      type TEXT NOT NULL DEFAULT 'project',
+      theme_id TEXT,
+      config TEXT,
+      tools TEXT,
+      is_default INTEGER DEFAULT 0,
+      is_system INTEGER DEFAULT 0,
+      show_in_toolbar INTEGER DEFAULT 0,
+      toolbar_icon TEXT,
+      toolbar_order INTEGER DEFAULT 99,
+      created_at TEXT DEFAULT CURRENT_TIMESTAMP,
+      updated_at TEXT DEFAULT CURRENT_TIMESTAMP
+    )
+  `)
+
+  // Canvas-components relation table
+  db.run(`
+    CREATE TABLE IF NOT EXISTS canvas_components (
+      id INTEGER PRIMARY KEY AUTOINCREMENT,
+      canvas_id TEXT NOT NULL,
+      component_id TEXT NOT NULL,
+      position INTEGER DEFAULT 0,
+      props TEXT,
+      layout TEXT,
+      is_visible INTEGER DEFAULT 1,
+      created_at TEXT DEFAULT CURRENT_TIMESTAMP,
+      UNIQUE(canvas_id, component_id)
+    )
+  `)
+
+  // Run column migrations for existing tables
+  runColumnMigrations(db)
+}
+
+function runColumnMigrations(db: Database) {
+  // Add toolbar columns to project_canvas if missing
+  const alterStatements = [
+    'ALTER TABLE project_canvas ADD COLUMN show_in_toolbar INTEGER DEFAULT 0',
+    'ALTER TABLE project_canvas ADD COLUMN toolbar_icon TEXT',
+    'ALTER TABLE project_canvas ADD COLUMN toolbar_order INTEGER DEFAULT 99'
+  ]
+
+  for (const sql of alterStatements) {
+    try {
+      db.run(sql)
+    } catch {
+      // Column already exists
+    }
+  }
+}