docs: document server settings API and add API test writing skill

Move the server settings roadmap to implemented/ rewritten per
the documentation standard (architecture and PUT flow diagrams,
endpoint table, design notes). Add a skill covering the pytest
conftest fixture model and the shared-client order-dependency
trap hit while writing the settings tests.

docs/gns3-copilot/roadmap/server-settings-api-roadmap.md

@@ -1,67 +0,0 @@
-<!--
-SPDX-License-Identifier: CC-BY-SA-4.0
-See LICENSE file for licensing information.
--->
-
-> This document is a roadmap/planning document. The described features have not been implemented yet.
-
-
-# Server Settings REST API — Roadmap
-
-## Problem
-
-Currently, `gns3_server.conf` can only be modified by directly editing the file on disk. There is no REST API endpoint to read or write server configuration, which prevents the Web UI from offering a settings page for server parameters.
-
-## Proposed API
-
-```
-GET  /v3/settings  →  Return all current server settings
-PUT  /v3/settings  →  Update and persist server settings
-```
-
-### Implementation Plan
-
-**1. Add `save_config()` to `Config` class** (`gns3server/config.py`)
-
-The `Config` class currently only reads configuration (via `read_config()` / `reload()`). A `save_config()` method is needed to serialize the in-memory `ServerConfig` pydantic model back to INI format and write it to disk.
-
-Serialization details:
-- `bool` → `"True"` / `"False"` (configparser convention)
-- `SecretStr` → `get_secret_value()`
-- `Enum` → `.value`
-- `List[str]` → semi-colon for `additional_images_paths`, comma for `allowed_interfaces`
-- `None` → skip
-
-**2. Add a settings getter/setter** to `Config` to allow programmatic updates to the in-memory settings.
-
-**3. New route file** (`gns3server/api/routes/controller/settings.py`):
-
-- `GET /v3/settings` — returns the full `ServerConfig` as JSON (pydantic automatically masks `SecretStr` fields as `"********"`)
-- `PUT /v3/settings` — accepts `ServerConfig`, merges existing secrets when placeholder values (`"********"`) are submitted, calls `save_config()`, and triggers runtime config update callbacks
-
-Both endpoints require `get_current_active_user` for authentication.
-
-**4. Register the new router** in `gns3server/api/routes/controller/__init__.py` under the `/settings` prefix.
-
-### Security
-
-- All settings endpoints require admin authentication (`get_current_active_user`)
-- `SecretStr` fields (`compute_password`, `default_admin_password`, `jwt_secret_key`) are masked in responses
-- On write, unchanged secrets are preserved via placeholder detection
-
-### Related Files
-
-| File | Role |
-|------|------|
-| `gns3server/config.py` | Config singleton with `read_config()` / `reload()` |
-| `gns3server/schemas/config.py` | `ServerConfig` pydantic model with all 9 sub-models |
-| `gns3server/api/routes/controller/__init__.py` | Controller router mounting |
-| `gns3server/controller/__init__.py` | `Controller._update_config()` for runtime credential sync |
-
-## Status
-
-- [ ] gns3server/config.py: add `save_config()` method
-- [ ] gns3server/config.py: add settings getter/setter
-- [ ] gns3server/api/routes/controller/settings.py: new route file with GET and PUT endpoints
-- [ ] gns3server/api/routes/controller/__init__.py: register settings router under `/settings`
-- [ ] gns3server/api/routes/controller/controller.py: add notification emission on config change