feat: project overview + timeline + docs center

- services/task_project_linker.py: task<->project mapping (title keywords + workspace_path)
- routes/pages.py: /timeline, /docs, /docs/<path>, enhanced /projects/<name> and /tasks/<id>
- templates: timeline.html, docs.html, doc_view.html (new), project_detail.html + task_detail.html (overhauled)
- config.py: DOCS_DIRS + ProjectConfig color
- base.html: Timeline + Docs nav links

templates/dashboard.html

@@ -123,7 +123,7 @@
     </form>
 </div>
 
-<h2 class="mt-20">📦 Project Status</h2>
+<h2 class="mt-20">📦 Project Overview</h2>
 <div class="card">
     <table>
         <thead>