fix: post-then-cleanup flow, remove dead code, pagination

- PostReview now returns *Review (id + user login from response)
- Delete flow: post first, then delete stale reviews by same user
- No read:user scope needed (identity from POST response)
- Removed GetAuthenticatedUser (requires scope we lack)
- ListReviews: full pagination (loops until partial page)
- envOrDefaultBool: case-insensitive, whitespace-trimmed
- action.yml: document accepted boolean values
- Tests updated for new PostReview signature

.gitea/actions/review/action.yml

@@ -67,7 +67,7 @@ inputs:
     required: false
     default: 'false'
   update-existing:
-    description: 'Delete previous review from same bot before posting (default true)'
+    description: 'Delete previous review from same bot before posting. Accepts: true/1/yes or false/0/no (default true)'
     required: false
     default: 'true'