feat: integrate user manual into help section

README.md

@@ -9,6 +9,7 @@ This README is intended for developers maintaining the project, not for end user
 - Python 3
 - Flask 2.3.3
 - Flask-HTTPAuth 4.8.0
+- markdown-it-py 3.0.0 for server-side Markdown rendering
 - Vanilla HTML, CSS, and JavaScript
 - JSON files for product data and forklift/load rules
 
@@ -58,7 +59,9 @@ The app uses HTTP Basic Auth. Current users are defined in `BETA_USERS` in `app.
 ├── fix_article_data.py
 ├── service-worker.js
 ├── templates/
-│   └── roll_calculator.html
+│   ├── help_index.html
+│   ├── roll_calculator.html
+│   └── user_manual.html
 ├── static/
 │   ├── article-data.json
 │   ├── config.json
@@ -71,6 +74,9 @@ The app uses HTTP Basic Auth. Current users are defined in `BETA_USERS` in `app.
 │   ├── rollcalc_stddev_ranges.js
 │   └── rollcalc_stddev_integration.js
 └── docs/
+    ├── de/
+    │   ├── screenshots/
+    │   └── user_manual.md
     ├── DEPLOYMENT_GUIDE.md
     ├── QOL_UPDATE_SUMMARY.md
     ├── STDDEV_IMPLEMENTATION_CHECKLIST.md
@@ -86,6 +92,9 @@ Implemented routes:
 | Route | Methods | Auth | Purpose |
 | --- | --- | --- | --- |
 | `/` | `GET` | Basic Auth | Renders `templates/roll_calculator.html`. |
+| `/help` | `GET` | Basic Auth | Renders the Help landing page. |
+| `/help/user-manual` | `GET` | Basic Auth | Reads `docs/de/user_manual.md`, renders it as HTML, and displays it in the RollCalc Help layout. |
+| `/help/user-manual/screenshots/<path:filename>` | `GET` | Basic Auth | Serves German user-manual screenshots from `docs/de/screenshots/` only. |
 | `/static/<path:filename>` | `GET` | Basic Auth | Intended protected static-file serving from `static/`. |
 | `/api/health` | `GET` | Basic Auth | Returns app health and version. |
 | `/api/user` | `GET` | Basic Auth | Returns current authenticated user info. |
@@ -109,6 +118,41 @@ Do not commit real passwords or print them in logs.
 
 Access logging is handled by `log_access()`, which reads `access_log.json`, appends a record, and writes the whole file back.
 
+## Help and User Manual
+
+RollCalc exposes an authenticated Help area at:
+
+```text
+/help
+```
+
+The user manual is available at:
+
+```text
+/help/user-manual
+```
+
+`docs/de/user_manual.md` is the leading source for the German user manual. The app reads this Markdown file on request and renders it server-side with `markdown-it-py`; no generated static HTML copy is maintained. Raw HTML in the Markdown source is disabled during rendering.
+
+The documentation directory is prepared for additional languages:
+
+```text
+docs/
+  de/
+    user_manual.md
+    screenshots/
+```
+
+The public route `/help/user-manual` currently opens the German manual. No language switcher is implemented yet.
+
+Screenshots referenced from the manual as `screenshots/filename.png` should be placed in:
+
+```text
+docs/de/screenshots/
+```
+
+The application rewrites those relative Markdown image paths to the authenticated manual screenshot route, which is limited to the active language's screenshot directory.
+
 ## Frontend Entry Point
 
 The active UI is `templates/roll_calculator.html`.