Add MkDocs configuration and documentation rules for TrackGo

- Created a new `mkdocs.yml` file to define the structure and navigation for technical documentation.
- Updated `doc-updater.md` to clarify the role of the documentation specialist and the split between technical and user documentation.
- Introduced new rules in `documentation.mdc` and `technical-docs.mdc` to guide the creation of documentation, emphasizing the separation of technical and user content.
- Added a `readme.md` in the `docs` directory to provide instructions for using MkDocs with Backstage.

.cursor/rules/documentation.mdc

@@ -0,0 +1,24 @@
+---
+description: TrackGo docs split — technical MkDocs here, user VitePress in trackgo-fe/apps/docs-dev
+alwaysApply: true
+---
+
+# Documentation Split
+
+TrackGo has two documentation kinds. Sibling repos: `trackgo-be`, `trackgo-fe`, `trackgo_mobile`.
+
+| Kind | Audience | Location | Tooling |
+| --- | --- | --- | --- |
+| Technical | Developers / engineers | `docs/` + `mkdocs.yml` (this repo) | MkDocs / Backstage TechDocs |
+| User | Customers / operators | `trackgo-fe/apps/docs-dev/` | VitePress |
+
+## Rules
+
+- Technical: stack, architecture, how to run, how modules interact (backend, web, landing, mobile).
+- User: features and usage (web + mobile only). Never put user how-tos in MkDocs.
+- Never put tech stack / package architecture / Electron IPC in docs-dev (user docs only going forward).
+- No emoji in any documentation.
+- Diagrams and sequence diagrams: PlantUML fenced blocks (` ```plantuml `), not Mermaid.
+- Source of truth is the codebase. If a brief disagrees with code, follow the code or label **Coming soon**. Do not invent features.
+
+Authoring details: `.cursor/rules/technical-docs.mdc` (when editing `docs/` or `mkdocs.yml`).

.cursor/rules/technical-docs.mdc

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+---
+description: How to write TrackGo technical docs in MkDocs (docs/ + mkdocs.yml)
+globs: docs/**/*.md,mkdocs.yml
+alwaysApply: false
+---
+
+# Technical Documentation (MkDocs)
+
+Audience: developers and engineers. Location: `docs/` + `mkdocs.yml`.
+
+## Scope
+
+Document tech stack, architecture, how to run, and how modules interact for:
+
+| Area | Sources |
+| --- | --- |
+| Backend | this repo — `src/app.module.ts`, `src/modules/` |
+| Frontend web | sibling `trackgo-fe/apps/web` |
+| Frontend landing | sibling `trackgo-fe/apps/landing` (public SPA, not the ERP) |
+| Mobile | sibling `trackgo_mobile` |
+
+Do **not** write customer how-tos here — those belong in `trackgo-fe/apps/docs-dev`.
+
+## Layout
+
+Prefer these folders under `docs/`:
+
+```text
+docs/
+  backend/
+  frontend-web/
+  frontend-landing/
+  mobile/
+  api.md              # keep existing API reference
+  report-*.md         # keep existing report docs
+```
+
+When adding pages:
+
+1. Create the markdown under the matching folder.
+2. Register it in `mkdocs.yml` `nav`.
+3. Set `site_name` to TrackGo (it may still say `Concourse CI` — rename when you touch nav).
+
+Preview: Docker TechDocs command in `docs/readme.md`.
+
+## Ground in code
+
+- Backend modules from `src/app.module.ts`: Auth, Users, Privileges, Configuration, Sales, Field, Reports.
+- Web menus / RBAC keys: `trackgo-fe/apps/web/src/apps/main/layouts/data/menu.data.ts`.
+- Mobile routes: `trackgo_mobile/lib/config/router.dart` (login, home, plan, customers, check-in, payment).
+- Cross-read sibling repos; do not invent features. Brief vs code → follow code or **Coming soon**.
+
+## Style
+
+- No emoji.
+- Diagrams / sequences: PlantUML only.
+
+````markdown
+```plantuml
+@startuml
+Alice -> Bob: request
+Bob --> Alice: response
+@enduml
+```
+````
+
+```text
+# BAD — user how-to in MkDocs
+docs/how-to-create-invoice.md
+
+# BAD — Mermaid or emoji
+```mermaid
+```
+"🚀 Getting Started"
+
+# GOOD
+docs/backend/architecture.md
+docs/frontend-web/modules.md
+```