Complete rewrite and re-architecture Osmedeus Engine in v5

docs/api/settings.md

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+# Settings
+
+Manage server configuration settings.
+
+## Get YAML Configuration
+
+Get the entire YAML configuration file with sensitive fields redacted. Fields containing `_key`, `secret`, `password`, `username`, or `_token` are replaced with `[REDACTED]`.
+
+```bash
+curl http://localhost:8002/osm/api/settings/yaml \
+  -H "Authorization: Bearer $TOKEN"
+```
+
+**Response:** (text/yaml)
+```yaml
+# =============================================================================
+# Osmedeus Configuration File
+# =============================================================================
+base_folder: ~/osmedeus-base
+
+environments:
+  binaries_path: "{{base_folder}}/binaries"
+  # ... more config
+
+server:
+  host: "0.0.0.0"
+  port: 8002
+  workspace_prefix_key: "[REDACTED]"
+  simple_user_map_key: "[REDACTED]"
+  jwt:
+    secret_signing_key: "[REDACTED]"
+    expiration_minutes: 180
+
+database:
+  host: ""
+  port: 5432
+  username: "[REDACTED]"
+  password: "[REDACTED]"
+  # ... more config
+```
+
+---
+
+## Update YAML Configuration
+
+Replace the entire YAML configuration file with new content. A backup of the existing configuration is created before overwriting.
+
+```bash
+curl -X PUT http://localhost:8002/osm/api/settings/yaml \
+  -H "Authorization: Bearer $TOKEN" \
+  -H "Content-Type: text/yaml" \
+  --data-binary @new-config.yaml
+```
+
+**Request Body:** Raw YAML configuration content
+
+**Response:**
+```json
+{
+  "message": "Configuration updated successfully",
+  "path": "/home/user/osmedeus-base/osm-settings.yaml",
+  "backup": "/home/user/osmedeus-base/osm-settings.yaml.backup"
+}
+```
+
+**Error Response (Invalid YAML):**
+```json
+{
+  "error": true,
+  "message": "Invalid YAML configuration: yaml: unmarshal errors: ..."
+}
+```