feat: add darkMode and hideSelectors screenshot parameters

- darkMode: emulates prefers-color-scheme: dark before navigation
- hideSelectors: injects CSS to hide elements before capture
  - POST: accepts string or string array
  - GET: accepts comma-separated string
  - Validation: max 10 selectors, each max 200 chars
- OpenAPI docs updated for both GET and POST endpoints
- 13 new tests added (service + route)

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "snapapi",
-  "version": "0.6.0",
+  "version": "0.7.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "snapapi",
-      "version": "0.6.0",
+      "version": "0.7.0",
       "dependencies": {
         "compression": "^1.8.1",
         "express": "^4.21.0",