feat: migrate default config and templates to npm specifiers

- quartz.config.default.yaml: all 44 plugins use @quartz-community/* npm specifiers
- cli/templates/*.yaml: all 4 templates updated (default, blog, obsidian, ttrpg)
- bootstrap-cli.mjs: updated help text
- package.json: devDeps use npm semver ranges instead of github: specifiers
- gitLoader.ts: regeneratePluginIndex scans npm packages from node_modules
- install-plugins.ts: generates plugin index for npm packages
- Removed quartz.lock.json (only relevant for git-installed plugins)

quartz/bootstrap-cli.mjs

@@ -40,7 +40,7 @@ async function launchTui() {
   if (!existsSync(tuiPath)) {
     console.error(
       "TUI plugin not installed. Install with:\n" +
-        "  npx quartz plugin add github:quartz-community/tui\n",
+        "  npx quartz plugin add @quartz-community/tui\n",
     )
     process.exit(1)
   }