fix(gitea): ensure consistent lastErr return for network errors

Move lastErr assignment outside the retry condition so that both
network errors and HTTP 5xx paths return lastErr consistently.

Previously, on the final retry attempt, a network error would return
the raw err variable instead of lastErr. While they held the same
value in practice, the inconsistency was confusing when reading the
code.

Now both paths:
- Network errors: assign lastErr before checking retry, return lastErr
- HTTP 5xx: assign lastErr before checking retry, return lastErr

Addresses review finding #3 (MINOR) from sonnet review on PR #69.

gitea/client.go

@@ -374,19 +374,21 @@ func (c *Client) doGet(ctx context.Context, reqURL string) ([]byte, error) {
 
 		resp, err := c.http.Do(req)
 		if err != nil {
-			// Check if this is a temporary/transient network error worth retrying.
-			// We only retry if there are attempts remaining.
+			// Always capture the error for consistent return at loop end.
+			// This ensures both network errors and HTTP 5xx return lastErr.
+			lastErr = err
+
+			// Only retry temporary network errors when attempts remain.
 			if attempt < maxAttempts-1 && isTemporaryNetError(err) {
 				slog.Warn("temporary network error, will retry",
 					"attempt", attempt+1,
 					"url", redactURL(reqURL),
 					"error", err)
-				lastErr = err
 				continue
 			}
-			return nil, err
+			// Non-retryable network error or final attempt exhausted.
+			return nil, lastErr
 		}
-
 		if resp.StatusCode >= 200 && resp.StatusCode < 300 {
 			body, err := io.ReadAll(resp.Body)
 			resp.Body.Close()